26 Mar 2011 - Lab-Rat
Shockingly, sometimes RIP doesn’t just work when you set it up. Especially when you’re working with a time constraint, and under stress, like on the CCIE lab. Here’s a few tools to debug RIP and figure out what’s going on.
r1#debug ip routing
- Should provide no output if the routing protocols are configured correctly and stable. If you have flopping routes (usually redistribution problems), you’ll see it here.
r1#undebug all
- can be abbreviated u all. If you’re going to try a debug that could make the router unresponsive, this trick can save you from a reboot.
1. Type u all, then hit enter.
2. Enter the the potentially dangerous debug, i.e. debug ip packet detail
3. Hit enter to start the debug, then quickly up arrow twice, to recall the u all from the history.
4. Hit enter to stop the debug.
Usually the scrolling debug output would prevent you from typing in the full command, but most of the time you can at least get a couple of up arrows and a carriage return in.
r1#show ip route x.x.x.x
- check if route is in routing table
R1#show ip route 135.15.16.0
Routing entry for 135.15.16.0/24
Known via “connected”, distance 0, metric 0 (connected, via interface)
Redistributing via eigrp 20, rip
Advertised by rip
Routing Descriptor Blocks:
* directly connected, via FastEthernet0/1.40
Route metric is 0, traffic share count is 1
r1#show ip protocol
- view versions of rip sent/received, passive interfaces, networks/summarization, etc.
R1#show ip protocols
Routing Protocol is “rip”
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Sending updates every 30 seconds, next due in 23 seconds
Invalid after 180 seconds, hold down 180, flushed after 240
Redistributing: eigrp 20, rip
Default version control: send version 2, receive version 2
Interface Send Recv Triggered RIP Key-chain
FastEthernet0/1.50 2 2
Automatic network summarization is in effect
Maximum path: 4
Routing for Networks:
135.15.0.0
Passive Interface(s):
FastEthernet0/0
FastEthernet0/1
FastEthernet0/1.10
FastEthernet0/1.40
Serial0/0/0
Serial0/0/0.12
Serial0/0/0.14
Serial0/0/1
Loopback1
Loopback10
Loopback101
VoIP-Null0
Routing Information Sources:
Gateway Distance Last Update
135.15.12.2 120 00:23:03
135.15.21.2 120 00:00:07
Distance: (default is 120)
r1#show interface type/slot/port
- show if the line protocol is down, etc
R1#show int f0/1.50
FastEthernet0/1.50 is up, line protocol is up
Hardware is MV96340 Ethernet, address is 001b.53e5.1631 (bia 001b.53e5.1631)
Internet address is 135.15.21.1/24
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation 802.1Q Virtual LAN, Vlan ID 50.
ARP type: ARPA, ARP Timeout 04:00:00
Last clearing of “show interface” counters never
r1#debug ip rip
- view routing updates
Sample Output:
R1#debug ip rip
RIP protocol debugging is on
R1#
*Feb 24 18:51:10.435: RIP: sending v2 update to 224.0.0.9 via FastEthernet0/1.50 (135.15.21.1)
*Feb 24 18:51:10.435: RIP: build update entries
*Feb 24 18:51:10.435: 135.15.12.0/24 via 0.0.0.0, metric 1, tag 0
*Feb 24 18:51:10.435: 135.15.13.0/24 via 0.0.0.0, metric 1, tag 0
*Feb 24 18:51:10.435: 135.15.14.0/24 via 0.0.0.0, metric 1, tag 0
*Feb 24 18:51:10.435: 135.15.16.0/24 via 0.0.0.0, metric 1, tag 0
*Feb 24 18:51:10.435: 135.15.26.0/24 via 0.0.0.0, metric 2, tag 0
*Feb 24 18:51:10.435: 135.15.101.0/24 via 0.0.0.0, metric 1, tag 0
R1#
*Feb 24 18:52:42.083: RIP: received v2 update from 135.15.21.2 on FastEthernet0/1.50
*Feb 24 18:52:42.083: 135.15.12.0/24 via 0.0.0.0 in 1 hops
*Feb 24 18:52:42.083: 135.15.16.0/24 via 0.0.0.0 in 2 hops
*Feb 24 18:52:42.083: 135.15.20.0/24 via 0.0.0.0 in 2 hops
*Feb 24 18:52:42.083: 135.15.23.0/24 via 0.0.0.0 in 1 hops
*Feb 24 18:52:42.083: 135.15.25.0/24 via 0.0.0.0 in 1 hops
*Feb 24 18:52:42.083: 135.15.26.0/24 via 0.0.0.0 in 1 hops
*Feb 24 18:52:42.083: 135.15.35.0/24 via 0.0.0.0 in 2 hops
*Feb 24 18:52:42.083: 135.15.102.0/24 via 0.0.0.0 in 1 hops
*Feb 24 18:52:42.083: 135.15.103.0/24 via 0.0.0.0 in 2 hops
r1(config)#access-list 100 permit ip any host 255.255.255.255
r1(config)#access-list 100 permit ip any host 224.0.0.9
r1#debug ip packet 100 detail
- debugs against acl 100, which is RIP1 (broadcast), and RIP2 (multicast)
More reading:
Troubleshooting IP Routing Protocols