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Duplexing bug 881 router

Hi all,

Yesterday i ran into a strange problem.
I installed a Cisco 881 router behind a 2960 switch.
On both devices i configured 100mb full duplexing, so auto neg off.


Also i configured an IP on the interface.
So the interface now looks like this:

Router#sh run int fa4
Building configuration...

Current configuration : 94 bytes
!
interface FastEthernet4
ip address 172.16.0.2 255.255.255.248
duplex full
speed 100
end

But when i do a "sho ip route" note the IP address from Fa4 (wich should be directly connected) is not shown in the routing table:

Router#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, + - replicated route

Gateway of last resort is 10.100.3.1 to network 0.0.0.0

S*    0.0.0.0/0 [254/0] via 10.100.3.1
      10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
C        10.0.0.0/24 is directly connected, Vlan10
L        10.0.0.2/32 is directly connected, Vlan10
S        10.100.2.248/32 [254/0] via 10.100.3.1, Vlan63
C        10.100.3.0/24 is directly connected, Vlan63
L        10.100.3.29/32 is directly connected, Vlan63

Strange?
Also there is absolutely no L3 traffice possible to/from fa4.

So now lets set the port settings to auto/auto:

Router#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#interface FastEthernet4
Router(config-if)#dup auto
Router(config-if)#speed auto
Router(config-if)#end

After writing the config and reloading i checked again, and surprisingly:

Router#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, + - replicated route

Gateway of last resort is 10.100.3.1 to network 0.0.0.0

S*    0.0.0.0/0 [254/0] via 10.100.3.1
      10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
S        10.100.2.248/32 [254/0] via 10.100.3.1, Vlan63
C        10.100.3.0/24 is directly connected, Vlan63
L        10.100.3.29/32 is directly connected, Vlan63
      172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
C        172.16.0.0/29 is directly connected, FastEthernet4
L        172.16.0.2/32 is directly connected, FastEthernet4

The exact same problem occurs when replacing the 2960 switch to a non Cisco model.
So the problem must be in the 881.


Maybe irrelevant, but i performed al little trick with causes it to work temporarily.
Create a subinterface on Fa4.

Router#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#int fa4.700
Router(config-subif)#encapsulation do
Router(config-subif)#encapsulation dot1Q 700
Router(config-subif)# ip address 172.16.0.2 255.255.255.248
Router(config-subif)#end


When looking in  the routing table it shows the IP address local connected on the Fa4.700 subinterface.

Router#sh ip route | i 172.16.0
      172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
C        172.16.0.0/29 is directly connected, FastEthernet4.700
L        172.16.0.2/32 is directly connected, FastEthernet4.700

At this moment i deleted the subinterface and configured the IP address on Fa4 again:

Router#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#no int fa4.700
Router(config)#int fa4
Router(config-if)#ip address 172.16.0.2 255.255.255.248
Router(config-if)#
Router(config-if)#end

Voila:
Router#sh ip route | i 172.16.0
      172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
C        172.16.0.0/29 is directly connected, FastEthernet4
L        172.16.0.2/32 is directly connected, FastEthernet4

Now L3 traffic is possible to/from Fa4.
But after i reload or powercycle the router the exact same problem, no local connected ip address, and no L3 traffic.

Anyone else stumbled onto this?

Router#sh ver
Cisco IOS Software, C880 Software (C880DATA-UNIVERSALK9-M), Version 15.0(1)M4, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2010 by Cisco Systems, Inc.
Compiled Fri 29-Oct-10 00:02 by prod_rel_team

ROM: System Bootstrap, Version 12.4(15r)XZ2, RELEASE SOFTWARE (fc1)

Router uptime is 4 minutes
System returned to ROM by reload at 06:44:46 UTC Thu May 26 2011
System image file is "flash:c880data-universalk9-mz.150-1.M4.bin"
Last reload type: Normal Reload
Last reload reason: Reload Command

2 Replies 2

paolo bevilacqua
Hall of Fame
Hall of Fame

It's a known bug for the 88x.

Try 15.0(1)M5, or even 15.1 something.

riroe
Level 3
Level 3

Thank you for your question.  This community is for Cisco Small Business products and your question is in reference to a Cisco Enterprise  product.  Please post your question in the Cisco NetPro forums located here:

- Routers ----> Network Infrastructure Forum http://forum.cisco.com/eforum/servlet/NetProf;jsessionid=E0EEC3D9CB4E5165ED16933737822748.SJ3A?page=Network_Infrastructure_discussion

THANKS

Rick Roe

Csco Small Business Support

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