08-13-2002 12:30 AM - edited 03-02-2019 12:38 AM
I have 4 routers and 2 switches on the same subnet all connecting to a catalyst switch. Routers can ping to each other fine but can't trace to any other routers. It traces to catalyst switch and atm switch fine. I have EIGRP and BGP running on the routers. Has anyone come across bizzare situation like this? This only started happening after I introduced another router and unfortunately I can't take that router out. any suggestions or ideas will be greatly appreciated.
JK
08-13-2002 01:43 AM
are they all in the same VLAN ?
When you say it fails, do you mean that you don't even see the first hop ?
Or does it fail after a few hops ?
If so, does it always fail at the same device ?
What type of router is the new one ?
Do you have any ACL or firewall device that could block icmp or udp ?
08-13-2002 09:01 AM
they are all in vlan 1 and this is what I get when tracing
1 * * *
2 * * *
3 * * *
4 * * *
5 * * *
6 * * *
I do not have an acl applied on the interface I"m tracing to. here's what I have on the interface.
interface GigabitEthernet0/0/0
description Connected to CAT4003
ip address x.x.x.x y.y.y.y
no ip redirects
no ip unreachables
load-interval 30
negotiation auto
08-13-2002 05:05 AM
It may be a routing issue. Are you using a routing protocol (EIGRP, OSPF, etc...)? Perhaps when you introduced the new router, you introduced a routing loop.
08-13-2002 05:44 AM
The fact you can ping indicates no particular L3 problem unless you notice extensive delay times.
Bear in mind Cisoc uses UDP for traceroute hence you could have and access-list that is being hit with no icmp unreachables conf on interfaces.
I would debug the trace by using debug icmp to see you you get anything back from remote router... Eg:
ldvd1mr01#trace 135.136.28.50
Type escape sequence to abort.
Tracing the route to 135.136.28.50
1 192.247.3.1 0 msec 4 msec 0 msec
2 135.136.28.50 0 msec 0 msec 0 msec
Router1#
3w5d: ICMP: time exeeded rcvd from 192.247.3.1
3w5d: ICMP: time exeeded rcvd from 192.247.3.1
3w5d: ICMP: time exeeded rcvd from 192.247.3.1
3w5d: ICMP: dst (192.247.3.17) port unreachable rcv from 135.136.28.50
3w5d: ICMP: dst (192.247.3.17) port unreachable rcv from 135.136.28.50
3w5d: ICMP: dst (192.247.3.17) port unreachable rcv from 135.136.28.50
08-13-2002 05:52 AM
One more test you could do...
I have written an extended access-list for a particular destination host, below is the result of the trace..
ldvd1mr01#debug ip packet 101 detail
IP packet debugging is on (detailed) for access list 101
ldvd1mr01#
ldvd1mr01#
ldvd1mr01#term mon
ldvd1mr01#trace 135.136.28.50
Type escape sequence to abort.
Tracing the route to 135.136.28.50
1 192.247.3.1 0 msec 4 msec 0 msec
2 135.136.28.50 4 msec 0 msec 0 msec
ldvd1mr01#
3w5d: datagramsize=60, IP 35950: s=192.247.3.17 (local), d=135.136.28.50, totlen 28,
fragment 0, fo 0, cef process switched
3w5d: UDP src=37431, dst=33434
3w5d: datagramsize=60, IP 35950: s=192.247.3.17 (local), d=135.136.28.50 (Vlan28), t
otlen 28, fragment 0, fo 0, sending
3w5d: UDP src=37431, dst=33434
3w5d: datagramsize=92, IP 35950: s=192.247.3.17 (local), d=135.136.28.50 (Vlan28), t
otlen 28, fragment 0, fo 0, sending full packet
3w5d: UDP src=37431, dst=33434
3w5d: datagramsize=60, IP 35952: s=192.247.3.17 (local), d=135.136.28.50, totlen 28,
fragment 0, fo 0, cef process switched
3w5d: UDP src=36720, dst=33435
3w5d: datagramsize=60, IP 35952: s=192.247.3.17 (local), d=135.136.28.50 (Vlan28), t
otlen 28, fragment 0, fo 0, sending
3w5d: UDP src=36720, dst=33435
3w5d: datagramsize=92, IP 35952: s=192.247.3.17 (local), d=135.136.28.50 (Vlan28), t
otlen 28, fragment 0, fo 0, sending full packet
3w5d: UDP src=36720, dst=33435
3w5d: datagramsize=70, IP 35955: s=192.247.3.17 (local), d=135.136.28.50, totlen 28,
fragment 0, fo 0, cef process switched
3w5d: UDP src=38482, dst=33436
3w5d: datagramsize=70, IP 35955: s=192.247.3.17 (local), d=135.136.28.50 (Vlan28), t
otlen 28, fragment 0, fo 0, sending
3w5d: UDP src=38482, dst=33436
3w5d: datagramsize=92, IP 35955: s=192.247.3.17 (local), d=135.136.28.50 (Vlan28), t
otlen 28, fragment 0, fo 0, sending full packet
3w5d: UDP src=38482, dst=33436
3w5d: datagramsize=70, IP 35957: s=192.247.3.17 (local), d=135.136.28.50, totlen 28,
fragment 0, fo 0, cef process switched
3w5d: UDP src=40994, dst=33437
3w5d: datagramsize=70, IP 35957: s=192.247.3.17 (local), d=135.136.28.50 (Vlan28), t
otlen 28, fragment 0, fo 0, sending
3w5d: UDP src=40994, dst=33437
3w5d: datagramsize=92, IP 35957: s=192.247.3.17 (local), d=135.136.28.50 (Vlan28), t
otlen 28, fragment 0, fo 0, sending full packet
3w5d: UDP src=40994, dst=33437
3w5d: datagramsize=70, IP 35959: s=192.247.3.17 (local), d=135.136.28.50, totlen 28,
fragment 0, fo 0, cef process switched
3w5d: UDP src=39424, dst=33438
3w5d: datagramsize=70, IP 35959: s=192.247.3.17 (local), d=135.136.28.50 (Vlan28), t
otlen 28, fragment 0, fo 0, sending
3w5d: UDP src=39424, dst=33438
3w5d: datagramsize=92, IP 35959: s=192.247.3.17 (local), d=135.136.28.50 (Vlan28), t
otlen 28, fragment 0, fo 0, sending full packet
3w5d: UDP src=39424, dst=33438
3w5d: datagramsize=70, IP 35961: s=192.247.3.17 (local), d=135.136.28.50, totlen 28,
fragment 0, fo 0, cef process switched
3w5d: UDP src=33030, dst=33439
3w5d: datagramsize=70, IP 35961: s=192.247.3.17 (local), d=135.136.28.50 (Vlan28), t
otlen 28, fragment 0, fo 0, sending
3w5d: UDP src=33030, dst=33439
3w5d: datagramsize=92, IP 35961: s=192.247.3.17 (local), d=135.136.28.50 (Vlan28), t
otlen 28, fragment 0, fo 0, sending full packet
3w5d: UDP src=33030, dst=33439
08-13-2002 11:34 PM
do a 'sh ip route 135.136.28.50'.
What is the next-hop ip address ?
Can you ping it ?
can you do a trace to it ?
Could you check the config of this device and check ACL or sth preventing icmp messages.
Finally, if you don't see anything, put a sniffer on the vlan and see if this next-hop sends icmp messages back to the original router that issued the trace.
08-13-2002 11:12 PM
Can you ping all the intermediate routers/switches... maybe have you got the route back from the final router but not on the intermediate ones
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