EIGRP Using SLOW connection vice fast connection

[cybrsage]

I am perplexed. My router is choosing the slow conneciton over the fast connection for EIGRP routes.

This is a dual hub and spoke design, with all the sites having a full T1 to the main (all via S0/0/0.1) and only 256k to the backup (all via the S0/0/0.2). For spoke site A to talk to spoke site B, it would either use two T1 links through the main hub or two 256k links through the backup hub.

Here is my setup (IPs have been changed):

interface Serial0/0/0.1 point-to-point

bandwidth 1544

ip address 1.1.1.1 255.255.255.252

ip nbar protocol-discovery

ip policy route-map nachi

frame-relay interface-dlci 16

!

interface Serial0/0/0.2 point-to-point

bandwidth 256

ip address 2.2.2.2 255.255.255.252

ip bandwidth-percent eigrp 1 10

ip policy route-map nachi

no cdp enable

frame-relay interface-dlci 20

!

router eigrp 1

redistribute connected

redistribute static

passive-interface GigabitEthernet0/0

passive-interface GigabitEthernet0/1

network 1.1.1.0 0.0.0.255

network 2.2.2.0 0.0.0.255

no auto-summary

no eigrp log-neighbor-changes

neighbor 1.1.1.2 Serial0/0/0.1

neighbor 2.2.2.2 Serial0/0/0.2

!

route-map nachi permit 10

match ip address 2003

match length 92 92

set interface Null0

#show ip eigrp nei

IP-EIGRP neighbors for process 1

H Address Interface Hold Uptime SRTT RTO Q Seq

(sec) (ms) Cnt Num

1 1.1.1.2 Se0/0/0.1 14 00:00:22 1244 5000 3 547766

0 2.2.2.2 Se0/0/0.2 10 00:04:51 32 2850 0 408246

#show ip eigrp top

IP-EIGRP Topology Table for AS(1)/ID(1.1.1.1)

P 0.0.0.0/0, 1 successors, FD is 10516992

via 2.2.2.2 (10516992/61952), Serial0/0/0.2

P 3.3.3.0/30, 1 successors, FD is 11023872

via 2.2.2.2 (11023872/10511872), Serial0/0/0.2

HELP!

[cybrsage]

194 input errors in 20 minutes, no other errors. Uses an external CSU/DSU so I cannot check a cisco WIC. I cleared the counters after you mentioned possible line errors, since I have been messing with the router for a bit.

[John Blakley]

I would look on the other end to see if you're getting errors there too. Then I would have the provider look at the line.

[cybrsage]

No errors on that side, but I will have the provider fix the slowly incrimenting incoming errors at the spoke site.

I will put the result in this thread and close out with the problem solved and such after they are done testing.

Thanks for all your help so far!

[mlund · Accepted solution]

Hi

I suspect this can be a mtu issue.

I would recomend you to set the mtu size to 1500 on the atm side.

/Mikael

[cybrsage]

I changed the MTU to 1500 on the ATM subinterface and that fixed the problem!