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BGP Next-hop Change

Hi All,

I want to discuss a problem that I am facing in the BGP scenario.

The problem is that I have 2 ISP connections from a service provider which is terminating on 6509 VSS and our companies 2 routers and ASA is also connected to 6509 VSS.
 

R5 is creating a eBGP peering with R3 (Primary ISP) and R4 (Secondary ISP) and in same way R6 is having eBGP peering with R3 and R4.

I am using 2 default routes 1st with default AD towards R3 (Pri ISP) and 2nd with a higher AD value towards R4 (Sec ISP).

After this I had changed Next-hop with the help of route-map.So, that the traffic will hit on ASAs interface from WAN side.

The route-map for R3 is having a set IP next-hop of ASAs IP address x.x.x.10 and the route-map for R4 is having a set IP next-hop of ASAs 2nd interface IP address y.y.y.10 

So, now problem is when I use command on R5 to see which next-hop I am sending to customer(#sh ip bgp nei x.x.x.3 advertised-routes) than for R3 network it shows me the exact next-hop which I want of x.x.x.10 ASAs interfaces but when I use same command to check for R4 than the output is also same i.e. it is having the next-hop of ASAs IP x.x.x.10 even in my route-map I am having a entry to set next-hop for R4 is ASAs interface IP y.y.y.10

After this I used wireshark to capture packet and I also used debug but the output shows that next-hop is set for R4 is y.y.y.10

So, this is the problem i.e. in show output command it is showing wrong next-hop but in capturing it is acknowledging that it is using the next-hop mentioned in route-map.

This is my configuration on R5 and same is on R6 just IPs are like y.y.y.6

R5#

!
interface GigabitEthernet0/0
 description TO Primary ISP
 ip address x.x.x.5 255.255.255.248
 duplex auto
 speed auto
 no shut
!
interface GigabitEthernet0/1
 description To Secondary ISP
 ip address y.y.y.5 255.255.255.248
 duplex auto
 speed auto
 no shut
!
ip access-list standard BLOCK
 deny any

 
route-map as_prepend_secondary permit 10
 set ip next-hop y.y.y.10
!
route-map as_prepend_primary permit 10
  set ip next-hop x.x.x.10
!

router bgp AAAAA
 no synchronization
 bgp log-neighbor-changes
 network z.z.z.z mask 255.255.255.248
 timers bgp 10 30
 neighbor y.y.y.4 remote-as BBBBB
 neighbor y.y.y.4 route-map as_prepend_secondary out
 neighbor x.x.x.3 remote-as BBBBB
 neighbor x.x.x.3 route-map as_prepend_primary out
 distribute-list BLOCK in
 no auto-summary
!

ip route x.x.x.0 255.255.255.0 x.x.x.3
ip route y.y.y.0 255.255.255.0 y.y.y.3 2

 

This is the output of Debug on R6

BGP: TX IPv4 Unicast Wkr global 7 Cur Processing.
BGP: TX IPv4 Unicast Wkr global 7 Cur Attr change from 0x0 to 0x68F081C8.
*Sep 15 13:16:15.056: BGP(0): y.y.y.4 NEXT_HOP is set to y.y.y.10 by policy for net y.y.y.128,

 

 

Thanks & Regards,
Rahul Chhabra

  • WAN Routing and Switching
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