EIGRP Equal paths question

rshum · ‎09-28-2009

I have 2 links between my data center and my DR site. They are both 150mbs lines. When I lose one of my links (VLAN264), which is the primary path, the other path (VLAN254) never becomes the preferred path. I can't the MSFC's on the DR 6509's to route data over that link.

My colleague thinks we have an issue with the metrics but I think since the delay and bandwidth are the same for both links we shouldn't have to manually tune the metrics EIGRP should handle that and we have a larger issue in the way routing is being handled.

Anyone have any ideas?

Jon Marshall · ‎09-28-2009

Roland

If the metrics are the same then you should be using both links at the same time anyway.

Regardless of that -

1) are the etherchannels at the main site and the DR site L2 etherchannels.

2) When you do a "sh ip route" on one of the DR 6500s do you see 2 equal cost paths to the main site or 1.

3) If the link between the DR site and main site fails on vlan 264 then do you not see any routes via vlan 254 ?

There are a lot of things that are unclear but the key one at the moment is why do the DR switches not have 2 equal cost paths in their routing tables.

Jon

rshum · ‎09-28-2009

Jon

1) Yes they are all L2 Etherchannels

2) No I only get 1 route.

3) I don't believe so I get any routes via VLAN254 when the VLAN264 route fails.

Roland

Jon Marshall · ‎09-28-2009

Roland

Okay then we need to work out why you are not getting both routes.

On DR02 can you post the output of

1) "sh ip eigrp neighbor"

2) pick a subnet that is in the primary building

"sh ip route "

3) "sh ip eigrp topology

Even if the DR site preferred one path then once that path has been lost it should query for the other path.

It may well be you need to use IP SLA to keep track of which path is active as a L3 SVI will probably not go down even if the link does.

One other question about the etherchannels - are they trunk links ?

Jon

rshum · ‎09-28-2009

10

DR02#sho ip eig nei

IP-EIGRP neighbors for process 1173

H Address Interface Hold Uptime SRTT RTO Q Seq Type

(sec) (ms) Cnt Num

11 10.90.254.62 Vl264 14 1d14h 36 216 0 17198

2 10.90.24.130 Vl24 14 6w5d 7 200 0 132169

9 10.90.212.2 Vl212 12 44w4d 5 200 0 132159

10 10.90.210.2 Vl210 11 44w4d 7 200 0 132165

8 10.90.216.2 Vl216 14 44w4d 8 200 0 132163

7 10.90.218.2 Vl218 13 44w4d 7 200 0 132166

6 10.90.223.2 Vl223 10 44w4d 6 200 0 132167

5 10.90.214.2 Vl214 14 44w4d 7 200 0 132170

4 10.90.219.2 Vl219 14 44w4d 8 200 0 132162

3 10.90.208.2 Vl208 12 1y1w 6 200 0 132158

1 10.90.222.1 Vl222 14 2y20w 6 200 0 132164

0 10.90.221.2 Vl221 14 2y20w 6 200 0 132168

2)DR02#sho ip rou 10.90.88.0

Routing entry for 10.90.88.0/24

Known via "eigrp 1173", distance 90, metric 3072, type internal

Redistributing via eigrp 1173

Last update from 10.90.254.62 on Vlan264, 1d12h ago

Routing Descriptor Blocks:

* 10.90.254.62, from 10.90.254.62, 1d12h ago, via Vlan264

Route metric is 3072, traffic share count is 1

Total delay is 20 microseconds, minimum bandwidth is 1000000 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 1

3)DR02#sho ip eigrp top 10.90.88.0 255.255.255.0

IP-EIGRP topology entry for 10.90.88.0/24

State is Passive, Query origin flag is 1, 1 Successor(s), FD is 3072

Routing Descriptor Blocks:

10.90.254.62 (Vlan264), from 10.90.254.62, Send flag is 0x0

Composite metric is (3072/2816), Route is Internal

Vector metric:

Minimum bandwidth is 1000000 Kbit

Total delay is 20 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 1

10.90.223.2 (Vlan223), from 10.90.223.2, Send flag is 0x0

Composite metric is (3328/3072), Route is Internal

Vector metric:

Minimum bandwidth is 1000000 Kbit

Total delay is 30 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 2

10.90.218.2 (Vlan218), from 10.90.218.2, Send flag is 0x0

Composite metric is (3328/3072), Route is Internal

Vector metric:

Minimum bandwidth is 1000000 Kbit

Total delay is 30 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 2

10.90.210.2 (Vlan210), from 10.90.210.2, Send flag is 0x0

Composite metric is (3328/3072), Route is Internal

Vector metric:

Minimum bandwidth is 1000000 Kbit

Total delay is 30 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 2

Yes the Etherchannels are trunks.

I didn't consider that with the L3 SVI's. I thought that EIGRP would simply reconverge and use the remaining route.

Jon Marshall · ‎09-28-2009

Roland

You have no EIGRP neigborship running over lan 254 hence the reason that you are not seeing routes via the secondary link. It also accounts for the reason why when the primary link fails the secondary link it not used and DC02 never even queries down that link.

Can you post

1) "sh ip int br" from DR02 and CS02

2) "sh int gi3/48" from CS02

3) "sh int gi3/5" from DR02

note i'm assuming both the above are gig ports - you will need to adjust if they are not.

4) Also from both CS02 and DR02 can you post the "router eigrp .." config.

Jon

rshum · ‎09-28-2009

1) CS02# sho ip int brie

Interface IP-Address OK? Method Status Protocol

Vlan1 10.90.5.62 YES NVRAM up up

Vlan20 10.90.20.2 YES NVRAM up up

Vlan27 10.90.27.2 YES NVRAM up up

Vlan28 10.90.28.2 YES NVRAM up up

Vlan30 10.90.30.2 YES NVRAM up up

Vlan32 10.90.32.252 YES NVRAM up up

Vlan33 10.90.33.252 YES NVRAM up up

Vlan34 10.90.34.252 YES NVRAM up up

Vlan35 10.90.35.252 YES NVRAM up up

Vlan36 10.90.36.252 YES NVRAM up up

Vlan37 10.90.37.252 YES NVRAM up up

Vlan38 10.90.38.252 YES NVRAM up up

Vlan39 10.90.39.252 YES NVRAM up up

Vlan40 10.90.40.252 YES NVRAM up up

Vlan41 10.90.41.252 YES NVRAM up up

Vlan42 10.90.42.252 YES NVRAM up up

Vlan43 10.90.43.252 YES NVRAM up up

Vlan44 10.90.44.252 YES NVRAM up up

Vlan45 10.90.45.252 YES NVRAM up up

Vlan46 10.90.46.252 YES NVRAM up up

Vlan47 10.90.47.252 YES NVRAM up up

Vlan48 10.90.48.252 YES NVRAM up up

DR02#sho ip int brie

Interface IP-Address OK? Method Status Protocol

Vlan24 10.90.24.131 YES manual up up

Vlan208 10.90.208.3 YES NVRAM up up

Vlan210 10.90.210.3 YES NVRAM up up

Vlan212 10.90.212.3 YES NVRAM up up

Vlan214 10.90.214.3 YES NVRAM up up

Vlan216 10.90.216.3 YES NVRAM up up

Vlan218 10.90.218.3 YES NVRAM up up

Vlan219 10.90.219.3 YES NVRAM up up

Vlan221 10.90.221.3 YES NVRAM up up

Vlan222 10.90.222.2 YES NVRAM up up

Vlan223 10.90.223.3 YES NVRAM up up

Vlan264 10.90.254.61 YES manual up up

2)

CS02#sho int g3/48

GigabitEthernet3/48 is up, line protocol is up (connected)

Hardware is C6k 1000Mb 802.3, address is 0024.9798.7fdb (bia 0024.9798.7fdb)

Description:

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 1000Mb/s, media type is SX

input flow-control is off, output flow-control is off

Clock mode is auto

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:45, output 00:00:45, output hang never

Last clearing of "show interface" counters never

Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 699000 bits/sec, 623 packets/sec

5 minute output rate 6313000 bits/sec, 974 packets/sec

170455961 packets input, 25177255152 bytes, 0 no buffer

Received 7565405 broadcasts (3383536 multicasts)

0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 0 multicast, 0 pause input

rshum · ‎09-28-2009

DR02> (enable) sho po 3/5

Port Name Status Vlan Duplex Speed Type

----- -------------------- ---------- ---------- ------ ----- ------------

3/5 connected trunk full 1000 1000BaseSX

Port Security Violation Shutdown-Time Age-Time Max-Addr Trap IfIndex

----- -------- --------- ------------- -------- -------- -------- -------

3/5 disabled shutdown 0 0 1 disabled 168

Port Num-Addr Secure-Src-Addr Age-Left Last-Src-Addr Shutdown/Time-Left

----- -------- ----------------- -------- ----------------- ------------------

3/5 0 - - - - -

Port Broadcast-Limit Multicast Unicast Total-Drop

-------- --------------- --------- ------- --------------------

3/5 - - - 0

Port Send FlowControl Receive FlowControl RxPause TxPause

admin oper admin oper

----- -------- -------- --------- --------- ---------- ----------

3/5 desired off off off 0 0

4)

DR02 router eigrp

router eigrp 1173

network 10.0.0.0

no auto-summary

no eigrp log-neighbor-changes

!

ip classless

no ip forward-protocol udp netbios-dgm

ip route 64.46.197.0 255.255.255.0 10.90.6.200

no ip http server

CD02 eigrp

router eigrp 1173

network 10.90.251.0 0.0.0.255

network 10.0.0.0

eigrp router-id 10.90.251.254

no eigrp log-neighbor-changes

no auto-summary

redistribute static

nsf

!

ip classless

Jon Marshall · ‎09-28-2009

Roland

There is no vlan 254 interface on either CS02 or DR02. Is this is a typo.

The ports that connect CS02 to DR02 ie. 3/48 on CS02 and 3/5 on DR02 - are they in vlan 254 ?. If they are and you don't have a L3 SVI for vlan 254 on both switches then they will not form an EIGRP neighborship across that backup link.

Jon

rshum · ‎09-28-2009

Jon

1) Yes they are all L2 Etherchannels

2) No I only get 1 route.

3) I don't believe so I get any routes via VLAN254 when the VLAN264 route fails.

Roland