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New Member

BGP reload problem

Hello,

Picture the following diagram, one Nexus switch with 2 BGP peers, one is eBGP the other one is iBGP. It receives the default router from both, the the one from eBGP si prefered. When the eBGP peer is reloaded, the following events occur on the Nexus switch:

-it removes the default route from the eBGP peer and adds it from the iBGP

-then adds back the default route from the eBGP peer since it is not fully down, and removes the one from the iBGP

This is happening for about 30-40 seconds until the eBGP peer is completly down, the default route from the iBGP peer is kept and everything is stable.

During this interval, there is packet loss.

Are there ways to prevent this behaviour ? I would like force the Nexus to keep the iBGP route all the wime while the eBGP peer is in the process of reloading.

This is happening only when the eBGP peer is reloaded, if I just reove the physical link between them, then the iBGP route is added and kept.

Thank you

Tudor

  • WAN Routing and Switching
1 ACCEPTED SOLUTION

Accepted Solutions

BGP reload problem

Hi,

just an idea:

When I see:

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 121

Paths: (2 available, best #1)

Flags: (0x000002) on xmit-list, is not in urib

  Advertised path-id 1

  Path type: external, path is valid, received and used, is best path, is staled

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (metric 0) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

is pointing me to BGP Graceful restart feature

http://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ftbgpnsf.html

The document says

"If the BGP session is lost during the RP switchover, the NSF-aware BGP peer marks all the routes associated with the NSF-capable router as stale; however, it continues to use these routes to make forwarding decisions for a set period of time."

There could be an IOS bug advertising RP switchover even while the router is rebooting?

Possibly you could try to disable graceful restart capability on your router?

Best regards,

Milan

9 REPLIES
Hall of Fame Super Blue

Re: BGP reload problem

Tudor

The only thing i can think of is route dampening where you can suppress a flapping route and this only applies to EBGP learned routes not IBGP. But that souds like it might fit.. I don't know whether it would work, or whether you have already considered/tried it but it might be worth a look -

http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfbgp.html#wp1002395

Edit - i should say i have never had the need to use route dampening so i'm not saying for sure it is a solution but it sounds like it might fit your scenario.

Jon

Hall of Fame Super Blue

BGP reload problem

Tudor

Are you sure that what you think is happening is actually happening ?

What are the BGP timers on the nexus switches with your EBGP neighbor. If the nexus realises the route is lost then that it sounds like the EBGP router has removed the route. So why would it advertise it again.

Where does the EBGP get the default route from. Is it originated on the EBGP router or is it passed on from another EBGP router ?

What is happening with the actual peering between the nexus and EBGP, is it up all the time ?

Jon

New Member

BGP reload problem

Hi Jon,

The timers are 30 and 90 , the default route is originated by the EGBP router, and the peering is up. Only when the status of the peering is in CLOSING then the Nexus keeps the route from the IBGP peer.

Plese see the output below: 10.0.1.11 being the EGBP peer and  10.1.12.2 being the IBGP peer:

2013 Dec  5 12:28:56.937949 bgp: 65001 [6673] RIB: [IPv4 Unicast] BGP received rnh notification from URIB for tid 0x1, nh 10.0.11.1/32

2013 Dec  5 12:28:56.937961 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] Queuing RNH: 10.0.11.1/32 into critical updates list

2013 Dec  5 12:28:59.349153 bgp: 65001 [6673] (default) ADJ: 10.1.12.2 KEEPALIVE rcvd

2013 Dec  5 12:28:59.955585 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] Processing RNH notification for 10.0.11.1/32

2013 Dec  5 12:28:59.955698 bgp: 65001 [6673] (default) RNH: Adjusting recursion for next-hop 10.0.11.1

2013 Dec  5 12:28:59.955714 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] Resolving next_hop 10.0.11.1/32

2013 Dec  5 12:28:59.955754 bgp: fsrv_is_shared_intf_vdc(2215): srv_type: 2 vdc_id: 1

2013 Dec  5 12:28:59.955797 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, reachability changed, IGP cost changed, RNH epoch changed, reachable

2013 Dec  5 12:28:59.955816 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, updating 1 routes

2013 Dec  5 12:28:59.955831 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Triggering bestpath selection for 0.0.0.0/0 , flags=0x1000003a

2013 Dec  5 12:28:59.955887 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, scheduled 1 routes for bestpath

2013 Dec  5 12:28:59.955906 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, scheduled 1 routes for bestpath, triggers 54

2013 Dec  5 12:28:59.955942 bgp: 65001 [6673] (default) SUM: [IPv4 Unicast] Starting bestpath (xid 38)

2013 Dec  5 12:28:59.956072 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Allocating URIB buffer, xid 39

2013 Dec  5 12:28:59.956114 bgp: librpm 65001 [6673] invalid policy handle when checking policy readyness

2013 Dec  5 12:28:59.956130 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Begin select bestpath for 0.0.0.0/0, adv_all=0, cal_nth=0, install_to_rib=0, flags=0x10000038

2013 Dec  5 12:28:59.956157 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Sending route 0.0.0.0/0 to URIB

2013 Dec  5 12:28:59.956171 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast]: adding route 0.0.0.0/0 via 10.0.11.1

2013 Dec  5 12:28:59.956182 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Adding path to 0.0.0.0/0 via 10.0.11.1 in URIB (table-id 0x1)

2013 Dec  5 12:28:59.956197 bgp: fsrv_is_shared_intf_vdc(2215): srv_type: 2 vdc_id: 1

2013 Dec  5 12:28:59.956221 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Deleting path to 0.0.0.0/0 via 10.1.12.2:(null) in table 0x1 from URIB

2013 Dec  5 12:28:59.956235 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Updating path to 0.0.0.0/0 in URIB, nhs added 1, deleted 1

2013 Dec  5 12:28:59.956250 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Selected new bestpath 0.0.0.0/0 flags=0x10800018 rid=0.0.0.0 nh=10.0.11.1

2013 Dec  5 12:28:59.956265 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] 0.0.0.0/0 path#1: set to rid=0.0.0.0 nh=10.0.11.1, flags=0x6, changed=1

2013 Dec  5 12:28:59.956279 bgp: 65001 [6673] (default) BRIB: [IPv4 Unicast] 0.0.0.0/0, no Label AF

2013 Dec  5 12:28:59.956300 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Completed bestpath for 1 prefixes xid 39

2013 Dec  5 12:28:59.958537 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] Queuing RNH: 10.0.11.1/32 into critical updates list

2013 Dec  5 12:29:01.905354 bgp: 65001 [6673] (default) ADJ: 10.12.12.2 keepalive timer fired

2013 Dec  5 12:29:01.905473 bgp: 65001 [6673] (default) ADJ: 10.12.12.2 keepalive timer fired for peer

2013 Dec  5 12:29:01.905567 bgp: 65001 [6673] (default) ADJ: 10.12.12.2 next keepalive expiry due in 00:00:21

2013 Dec  5 12:29:01.905586 bgp: 65001 [6673] (default) ADJ: 10.2.11.2 keepalive timer fired

2013 Dec  5 12:29:01.905607 bgp: 65001 [6673] (default) ADJ: 10.2.11.2 keepalive timer fired for peer

2013 Dec  5 12:29:01.905639 bgp: 65001 [6673] (default) ADJ: 10.2.11.2 next keepalive expiry due in 00:00:21

2013 Dec  5 12:29:01.905655 bgp: 65001 [6673] (default) ADJ: 10.1.12.2 keepalive timer fired

2013 Dec  5 12:29:01.905672 bgp: 65001 [6673] (default) ADJ: 10.1.12.2 keepalive timer fired for peer

2013 Dec  5 12:29:01.905702 bgp: 65001 [6673] (default) ADJ: 10.1.12.2 next keepalive expiry due in 00:00:21

2013 Dec  5 12:29:02.979194 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] Processing RNH notification for 10.0.11.1/32

2013 Dec  5 12:29:02.979223 bgp: 65001 [6673] (default) RNH: Adjusting recursion for next-hop 10.0.11.1

2013 Dec  5 12:29:02.979239 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] Resolving next_hop 10.0.11.1/32

2013 Dec  5 12:29:02.979277 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, reachability changed, IGP cost changed, RNH epoch changed

2013 Dec  5 12:29:02.979292 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, updating 1 routes

2013 Dec  5 12:29:02.979310 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Triggering bestpath selection for 0.0.0.0/0 , flags=0x10000022

2013 Dec  5 12:29:02.979365 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, scheduled 1 routes for bestpath

2013 Dec  5 12:29:02.979383 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, scheduled 1 routes for bestpath, triggers 55

2013 Dec  5 12:29:02.979419 bgp: 65001 [6673] (default) SUM: [IPv4 Unicast] Starting bestpath (xid 39)

2013 Dec  5 12:29:02.979569 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Allocating URIB buffer, xid 40

2013 Dec  5 12:29:02.979619 bgp: librpm 65001 [6673] invalid policy handle when checking policy readyness

2013 Dec  5 12:29:02.979637 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Begin select bestpath for 0.0.0.0/0, adv_all=0, cal_nth=0, install_to_rib=0, flags=0x10000020

2013 Dec  5 12:29:02.979663 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Sending route 0.0.0.0/0 to URIB

2013 Dec  5 12:29:02.979678 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast]: adding route 0.0.0.0/0 via 10.1.12.2

2013 Dec  5 12:29:02.979689 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Adding path to 0.0.0.0/0 via 10.1.12.2 in URIB (table-id 0x1)

2013 Dec  5 12:29:02.979706 bgp: fsrv_is_shared_intf_vdc(2215): srv_type: 2 vdc_id: 1

2013 Dec  5 12:29:02.979733 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Deleting path to 0.0.0.0/0 via 10.0.11.1:(null) in table 0x1 from URIB

2013 Dec  5 12:29:02.979748 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Updating path to 0.0.0.0/0 in URIB, nhs added 1, deleted 1

2013 Dec  5 12:29:02.981817 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] Queuing RNH: 10.0.11.1/32 into critical updates list

2013 Dec  5 12:29:05.106716 bgp: 65001 [6673] (default) ADJ: 10.2.11.2 KEEPALIVE rcvd

2013 Dec  5 12:29:05.645361 bgp: 65001 [6673] (default) EVT: 10.0.11.1 peer connection retry timer expired

2013 Dec  5 12:29:05.645518 bgp: 65001 [6673] (default) EVT: Single hop EBGP peer 10.0.11.1 not directly attached (active), outbound interface Unknown

2013 Dec  5 12:29:05.995491 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] Processing RNH notification for 10.0.11.1/32

2013 Dec  5 12:29:05.995618 bgp: 65001 [6673] (default) RNH: Adjusting recursion for next-hop 10.0.11.1

2013 Dec  5 12:29:05.995633 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] Resolving next_hop 10.0.11.1/32

2013 Dec  5 12:29:05.995670 bgp: fsrv_is_shared_intf_vdc(2215): srv_type: 2 vdc_id: 1

2013 Dec  5 12:29:05.995709 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, reachability changed, IGP cost changed, RNH epoch changed, reachable

2013 Dec  5 12:29:05.995728 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, updating 1 routes

2013 Dec  5 12:29:05.995742 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Triggering bestpath selection for 0.0.0.0/0 , flags=0x1000003a

2013 Dec  5 12:29:05.995797 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, scheduled 1 routes for bestpath

2013 Dec  5 12:29:05.995817 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, scheduled 1 routes for bestpath, triggers 56

2013 Dec  5 12:29:05.995852 bgp: 65001 [6673] (default) SUM: [IPv4 Unicast] Starting bestpath (xid 40)

2013 Dec  5 12:29:05.995976 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Allocating URIB buffer, xid 41

2013 Dec  5 12:29:05.996016 bgp: librpm 65001 [6673] invalid policy handle when checking policy readyness

2013 Dec  5 12:29:05.996032 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Begin select bestpath for 0.0.0.0/0, adv_all=0, cal_nth=0, install_to_rib=0, flags=0x10000038

2013 Dec  5 12:29:05.996056 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Sending route 0.0.0.0/0 to URIB

2013 Dec  5 12:29:05.996071 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast]: adding route 0.0.0.0/0 via 10.0.11.1

2013 Dec  5 12:29:05.996084 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Adding path to 0.0.0.0/0 via 10.0.11.1 in URIB (table-id 0x1)

2013 Dec  5 12:29:05.996097 bgp: fsrv_is_shared_intf_vdc(2215): srv_type: 2 vdc_id: 1

2013 Dec  5 12:29:05.996121 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Deleting path to 0.0.0.0/0 via 10.1.12.2:(null) in table 0x1 from URIB

2013 Dec  5 12:29:05.996133 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Updating path to 0.0.0.0/0 in URIB, nhs added 1, deleted 1

2013 Dec  5 12:29:05.996148 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Selected new bestpath 0.0.0.0/0 flags=0x10800018 rid=0.0.0.0 nh=10.0.11.1

2013 Dec  5 12:29:05.996161 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] 0.0.0.0/0 path#1: set to rid=0.0.0.0 nh=10.0.11.1, flags=0x6, changed=1

2013 Dec  5 12:29:05.996175 bgp: 65001 [6673] (default) BRIB: [IPv4 Unicast] 0.0.0.0/0, no Label AF

2013 Dec  5 12:29:05.996195 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Completed bestpath for 1 prefixes xid 41

2013 Dec  5 12:29:05.998201 bgp: 65001 [6673] RIB: [IPv4 Unicast] BGP received rnh notification from URIB for tid 0x1, nh 10.0.11.1/32

2013 Dec  5 12:29:05.998221 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] Queuing RNH: 10.0.11.1/32 into critical updates list

2013 Dec  5 12:29:07.606445 bgp: 65001 [6673] (default) ADJ: 10.12.12.2 KEEPALIVE rcvd

2013 Dec  5 12:29:09.015460 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] Processing RNH notification for 10.0.11.1/32

2013 Dec  5 12:29:09.015608 bgp: 65001 [6673] (default) RNH: Adjusting recursion for next-hop 10.0.11.1

2013 Dec  5 12:29:09.015624 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] Resolving next_hop 10.0.11.1/32

2013 Dec  5 12:29:09.015658 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, reachability changed, IGP cost changed, RNH epoch changed

2013 Dec  5 12:29:09.015678 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, updating 1 routes

2013 Dec  5 12:29:09.015693 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Triggering bestpath selection for 0.0.0.0/0 , flags=0x10000022

2013 Dec  5 12:29:09.015748 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, scheduled 1 routes for bestpath

2013 Dec  5 12:29:09.015766 bgp: 65001 [6673] (default) RNH: [IPv4 Unicast] next-hop 10.0.11.1/32, scheduled 1 routes for bestpath, triggers 57

2013 Dec  5 12:29:09.015802 bgp: 65001 [6673] (default) SUM: [IPv4 Unicast] Starting bestpath (xid 41)

2013 Dec  5 12:29:09.015847 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Allocating URIB buffer, xid 42

2013 Dec  5 12:29:09.015884 bgp: librpm 65001 [6673] invalid policy handle when checking policy readyness

2013 Dec  5 12:29:09.016006 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Begin select bestpath for 0.0.0.0/0, adv_all=0, cal_nth=0, install_to_rib=0, flags=0x10000020

2013 Dec  5 12:29:09.016033 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Sending route 0.0.0.0/0 to URIB

2013 Dec  5 12:29:09.016045 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast]: adding route 0.0.0.0/0 via 10.1.12.2

2013 Dec  5 12:29:09.016056 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Adding path to 0.0.0.0/0 via 10.1.12.2 in URIB (table-id 0x1)

2013 Dec  5 12:29:09.016073 bgp: fsrv_is_shared_intf_vdc(2215): srv_type: 2 vdc_id: 1

2013 Dec  5 12:29:09.016101 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Deleting path to 0.0.0.0/0 via 10.0.11.1:(null) in table 0x1 from URIB

2013 Dec  5 12:29:09.016116 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Updating path to 0.0.0.0/0 in URIB, nhs added 1, deleted 1

2013 Dec  5 12:29:09.016128 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Selected new bestpath 0.0.0.0/0 flags=0x10800000 rid=10.0.22.2 nh=10.1.12.2

2013 Dec  5 12:29:09.016141 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] 0.0.0.0/0 path#1: set to rid=10.0.22.2 nh=10.1.12.2, flags=0x6, changed=1

2013 Dec  5 12:29:09.016155 bgp: 65001 [6673] (default) BRIB: [IPv4 Unicast] 0.0.0.0/0, no Label AF

2013 Dec  5 12:29:09.016176 bgp: 65001 [6673] (default) RIB: [IPv4 Unicast] Completed bestpath for 1 prefixes xid 42

BGP reload problem

Hi,

is your eBGP neighbour using for peering an interface within a subnet directly connected to your Nexus?

As the debug mesages are talking about RNH = Recursive Next Hop I believe?

Best regards,

Milan

New Member

BGP reload problem

Hi Milan,

Yes the EBGP peer is directly connected, it is an ASR..

Some additional debug to confirm the events, how the N7K is choosing between paths, when path#2 is chosen, I have replies from downstream hosts, but when pach#1 is chosen back, I have downtime and it stays like this for 30-40 secs.

I have tried to lowe the bgp timers, to implement BFD, but no effect.. I ll try to use dampening although I wouldn't prefer it..

Regards,

Tudor

N7K-1# ping 10.0.11.1

PING 10.0.11.1 (10.0.11.1): 56 data bytes

Request 0 timed out

Request 1 timed out

ping: sendto 10.0.11.1 64 chars, No route to host

Request 2 timed out

Request 3 timed out

Request 4 timed out

--- 10.0.11.1 ping statistics ---

5 packets transmitted, 0 packets received, 100.00% packet loss

N7K-1# ^C

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 118

Paths: (2 available, best #2)

Flags: (0x00001a) on xmit-list, is in urib, is best urib route

  Path type: external, path is invalid, received and used, is staled, no labeled nexthop

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (inaccessible, metric 4294967295) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Advertised path-id 1

  Path type: internal, path is valid, received and used, is best path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 120

Paths: (2 available, best #2)

Flags: (0x00001a) on xmit-list, is in urib, is best urib route

  Path type: external, path is invalid, received and used, is staled, no labeled nexthop

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (inaccessible, metric 4294967295) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Advertised path-id 1

  Path type: internal, path is valid, received and used, is best path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 121

Paths: (2 available, best #1)

Flags: (0x000002) on xmit-list, is not in urib

  Advertised path-id 1

  Path type: external, path is valid, received and used, is best path, is staled

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (metric 0) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Path type: internal, path is valid, received and used, not best reason: Internal path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.1.12.2          10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 122

Paths: (2 available, best #2)

Flags: (0x00001a) on xmit-list, is in urib, is best urib route

  Path type: external, path is invalid, received and used, is staled, no labeled nexthop

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (inaccessible, metric 4294967295) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Advertised path-id 1

  Path type: internal, path is valid, received and used, is best path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 123

Paths: (2 available, best #1)

Flags: (0x000002) on xmit-list, is not in urib

  Advertised path-id 1

  Path type: external, path is valid, received and used, is best path, is staled

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (metric 0) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Path type: internal, path is valid, received and used, not best reason: Internal path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.1.12.2          10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 124

Paths: (2 available, best #2)

Flags: (0x00001a) on xmit-list, is in urib, is best urib route

  Path type: external, path is invalid, received and used, is staled, no labeled nexthop

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (inaccessible, metric 4294967295) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Advertised path-id 1

  Path type: internal, path is valid, received and used, is best path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 124

Paths: (2 available, best #2)

Flags: (0x00001a) on xmit-list, is in urib, is best urib route

  Path type: external, path is invalid, received and used, is staled, no labeled nexthop

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (inaccessible, metric 4294967295) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Advertised path-id 1

  Path type: internal, path is valid, received and used, is best path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 125

Paths: (2 available, best #1)

Flags: (0x000002) on xmit-list, is not in urib

  Advertised path-id 1

  Path type: external, path is valid, received and used, is best path, is staled

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (metric 0) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Path type: internal, path is valid, received and used, not best reason: Internal path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.1.12.2          10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 125

Paths: (2 available, best #1)

Flags: (0x000002) on xmit-list, is not in urib

  Advertised path-id 1

  Path type: external, path is valid, received and used, is best path, is staled

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (metric 0) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Path type: internal, path is valid, received and used, not best reason: Internal path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.1.12.2          10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 127

Paths: (2 available, best #1)

Flags: (0x000002) on xmit-list, is not in urib

  Advertised path-id 1

  Path type: external, path is valid, received and used, is best path, is staled

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (metric 0) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Path type: internal, path is valid, received and used, not best reason: Internal path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.1.12.2          10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 128

Paths: (2 available, best #2)

Flags: (0x00001a) on xmit-list, is in urib, is best urib route

  Path type: external, path is invalid, received and used, is staled, no labeled nexthop

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (inaccessible, metric 4294967295) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Advertised path-id 1

  Path type: internal, path is valid, received and used, is best path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp sum

BGP summary information for VRF default, address family IPv4 Unicast

BGP router identifier 10.0.11.2, local AS number 65001

BGP table version is 131, IPv4 Unicast config peers 4, capable peers 3

7 network entries and 14 paths using 1176 bytes of memory

BGP attribute entries [8/1088], BGP AS path entries [2/12]

BGP community entries [0/0], BGP clusterlist entries [0/0]

12 received paths for inbound soft reconfiguration

12 identical, 0 modified, 0 filtered received paths using 0 bytes

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd

10.0.11.1       4 65000     736     751        0    0    0 00:01:47 Idle    

10.1.12.2       4 65001     219     266      131    0    0 01:31:03 7        

10.2.11.2       4 65002     185     261      131    0    0 01:30:05 1        

10.12.12.2      4 65002     186     263      131    0    0 01:31:01 3        

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 136

Paths: (2 available, best #2)

Flags: (0x00001a) on xmit-list, is in urib, is best urib route

  Path type: external, path is invalid, received and used, is staled, no labeled nexthop

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (inaccessible, metric 4294967295) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Advertised path-id 1

  Path type: internal, path is valid, received and used, is best path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 136

Paths: (2 available, best #2)

Flags: (0x00001a) on xmit-list, is in urib, is best urib route

  Path type: external, path is invalid, received and used, is deleted, no labeled nexthop

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (inaccessible, metric 4294967295) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Advertised path-id 1

  Path type: internal, path is valid, received and used, is best path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 137

Paths: (2 available, best #2)

Flags: (0x00001a) on xmit-list, is in urib, is best urib route

  Path type: external, path is invalid, received and used, is deleted, no labeled nexthop

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (metric 0) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

  Advertised path-id 1

  Path type: internal, path is valid, received and used, is best path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.2.11.2          10.12.12.2    

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 137

Paths: (1 available, best #1)

Flags: (0x00001a) on xmit-list, is in urib, is best urib route

  Advertised path-id 1

  Path type: internal, path is valid, received and used, is best path

  AS-Path: 65000 , path sourced external to AS

    10.1.12.2 (metric 0) from 10.1.12.2 (10.0.22.2)

      Origin IGP, MED not set, localpref 100, weight 0

  Path-id 1 advertised to peers:

    10.2.11.2          10.12.12.2

BGP reload problem

Hi,

just an idea:

When I see:

N7K-1# sh ip bgp 0.0.0.0

BGP routing table information for VRF default, address family IPv4 Unicast

BGP routing table entry for 0.0.0.0/0, version 121

Paths: (2 available, best #1)

Flags: (0x000002) on xmit-list, is not in urib

  Advertised path-id 1

  Path type: external, path is valid, received and used, is best path, is staled

  AS-Path: 65000 , path sourced external to AS

    10.0.11.1 (metric 0) from 10.0.11.1 (0.0.0.0)

      Origin IGP, MED not set, localpref 100, weight 0

is pointing me to BGP Graceful restart feature

http://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ftbgpnsf.html

The document says

"If the BGP session is lost during the RP switchover, the NSF-aware BGP peer marks all the routes associated with the NSF-capable router as stale; however, it continues to use these routes to make forwarding decisions for a set period of time."

There could be an IOS bug advertising RP switchover even while the router is rebooting?

Possibly you could try to disable graceful restart capability on your router?

Best regards,

Milan

New Member

BGP reload problem

Hi,

I have tried with/without graceful-restart feature with different restart/stal timers but no effect..

The annoying thing is that even if the bgp neighbour state is in IDLE, it still uses the route from it.Only when the state is CLOSING, the other route is prefered and kept...

Regards,

Tudor

New Member

BGP reload problem

Hi Milan,

You were right, I was disabling the feature only on the EBGP peer, but right after I have disable it on the Nexus, it worked just fine. The only thing left to do, is to test how it works when I perform a switch over between supervisors.

Thanks,

Regards,

Tudor

New Member

BGP reload problem

Just as an update, when the system switchover happens, with the graceful restart feature being disabled, there is not packet loss, although bgp goes down and comes up very fast.

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