02-21-2014 08:13 PM - edited 03-04-2019 10:24 PM
Hi Brothers and Sisters
I got a strangh routing problem on our 3750X which found that from the traceroute that some specific destination cannot route to the next hop IP configured in static route.
----------------------------------------- ------------------------------------- ----------------------------------------
| 3750-Office (10.1.99.198) | --(MetroE Circuit)---- | 3750-DC (10.1.99.199) | -------- | MPLS Router (10.1.1.30) |
------------------------------------------ -------------------------------------- ----------------------------------------
//Routing info of 192.168.100.240
C3750Xa-DataCenter#sh ip route 192.168.100.240
Routing entry for 192.168.96.0/21, supernet
Known via "static", distance 1, metric 0
Redistributing via rip
Advertised by rip
Routing Descriptor Blocks:
* 10.1.1.30
Route metric is 0, traffic share count is 1
//Routing info of 192.168.97.30 (This can route correctly)
C3750Xa-DataCenter#sh ip route 192.168.97.30
Routing entry for 192.168.96.0/21, supernet
Known via "static", distance 1, metric 0
Redistributing via rip
Advertised by rip
Routing Descriptor Blocks:
* 10.1.1.30
Route metric is 0, traffic share count is 1
However when traceroute to 192.168.100.240 it was found that routed to different nexthop IP.
//Traceroute to 192.168.100.240 Incorrect next hop IP
C3750Xa-DataCenter#traceroute 192.168.100.240
Type escape sequence to abort.
Tracing the route to 192.168.100.240
1 10.1.99.198 0 msec 8 msec 9 msec
2 10.11.1.2 8 msec 8 msec 0 msec
3 10.1.99.198 9 msec 0 msec 8 msec
4 10.11.1.2 9 msec 8 msec 0 msec
//Traceroute to 192.168.97.30 (Correct next hop IP)
C3750Xa-DataCenter#traceroute 192.168.97.30
Type escape sequence to abort.
Tracing the route to 192.168.97.30
1 10.1.1.30 8 msec 0 msec 9 msec
2 172.25.0.1 8 msec 8 msec 0 msec
3 172.25.1.1 235 msec 235 msec 226 msec
4 172.25.1.2 235 msec * 235 msec
And CEF table shows everything normal and to correct next hop.
//CEF to 192.168.100.240
C3750Xa-DataCenter#sh ip cef 192.168.100.240 d
192.168.96.0/21, epoch 3
recursive via 10.1.1.30
attached to Vlan10
//CEF to 192.168.97.30
C3750Xa-DataCenter#sh ip cef 192.168.97.30 d
192.168.96.0/21, epoch 3
recursive via 10.1.1.30
attached to Vlan10
Anyone whats the problem is? I guess there must be some problem in the FIB table, but I am not sure how to continue the troubleshooting.
Thx
Sunny Wong
02-22-2014 12:27 AM
Hello
Looks like you have recursive routing,
Is the 3780switch is obtaining the static via redistributing static command without the ip route 0.0.0.0 0.0.0.XXXX From the DC router? Default-originate would be a better choice if applicable.
Is there a gateway of last resort set?
What version of rip is running and is auto summarisation turned off if ripv2 is in use
On the 3780:
Sh ip route rip
Res
Paul
Sent from Cisco Technical Support iPad App
02-22-2014 03:57 AM
Hi Paul
Thanks for your reply. Am...you can saw from the "show ip route xxxx" output, it is a static route configured on the 3750 manually not by learning from RIP.
And both 192.168.100.240 and 192.168.97.xx are under the same supernet 192.168.96.0/21 and route to 10.1.1.30
However you can see from the traceroute, the 1st hop to 192.168.100.240 is routed to 10.1.99.198 which is not the next hop configured as static route.
Sunny
Sent from Cisco Technical Support iPhone App
02-22-2014 04:52 AM
Hello
Sent from Cisco Technical Support iPad App
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