[Xorp-users] cannot ping one of the interfaces from an OSPF router after installing XORP

[Avinash Sridharan]

Look at whats being programmed in the kernel route tables in router 5.
Something like "ip route show" command should give you the routing table
programmed in the linux kernel. It might give you some idea as to why the
ICMP response is not being sent out. Also, make sure the ARP cache on
router 5 has the ARPs resolve for 192.168.13.1 on router 5.


On Tue, Aug 5, 2014 at 8:32 AM, Liu, Xuan (UMKC-Student) <
xuan.liu at mail.umkc.edu> wrote:

>  Hello,
>
>
>  I have came across this problem when I have configured a simple
> five-node network running OSPF protocol. The topology looks like
>
>
>                    1 --------------- 2
>
>                 /  \                   / \
>
>               /      \               /    |
>
>               4       \           /       3
>
>               |         \        /        |
>
>                \          \     /        /
>
>                  \         \  /        /
>
>                    \------ 5 -----/
>
>
>  The link information is : rt1:eth4 -- rt2:eth1: 192.168.1.1 - 192.168.1.2
>
>                                         rt2:eth4 -- rt3:eth3: 192.168.6.1
> - 192.168.6.2
>
>                                         rt3:eth2 -- rt5:eth2: 192.168.10.1
> - 192.168.10.2
>
>                                         rt5:eth1 -- rt4:eth3: 192.168.13.2 -
> 192.168.13.1
>
>                                         rt4:eth2 -- rt1:eth2: 192.168.2.2
> - 192.168.2.1
>
>                                         rt1:eth3 -- rt5:eth3: 192.168.3.1
> - 192.168.3.2
>
>                                         rt2:eth2 -- rt5:eth5: 192.168.7.1
> - 192.168.7.2
>
> All link has prefix 24.
>
>
>  Each node runs Ubuntu 12.04 OS, and I have installed XORP 1.8.5. For
> each node, I have configured it as an OSPF router. Most of the routing
> looks fine to me, except for some interfaces. For example:
>
>
>  If I send ping request from rt1 to 192.168.7.2 (rt5), I got no response.
> The routing table at rt1, rt5 are like:
>
>
>  root at rt-1> show route table ipv4 unicast ospf
> 192.168.6.0/24 [ospf(110)/20]
> > to 192.168.1.2 via eth4/eth4
> 192.168.7.0/24 [ospf(110)/20]
> > to 192.168.1.2 via eth4/eth4
> 192.168.10.0/24 [ospf(110)/20]
> > to 192.168.3.2 via eth3/eth3
> 192.168.13.0/24 [ospf(110)/20]
> > to 192.168.2.2 via eth2/eth2
>
>
>
>  root at rt-5> show route table ipv4 unicast ospf
> 192.168.1.0/24 [ospf(110)/20]
> > to 192.168.3.1 via eth3/eth3
> 192.168.2.0/24 [ospf(110)/20]
> > to 192.168.3.1 via eth3/eth3
> 192.168.6.0/24 [ospf(110)/20]
> > to 192.168.10.1 via eth2/eth2
>
>
>  I ran tcpdump at rt1, rt2 and rt5 and found that
>
>
>  At rt-2 eth1:
>  xuanliu at rt-2:~$ sudo tcpdump -i eth1 icmp -n
> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
> listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes
> 11:22:58.797404 IP 192.168.1.1 > 192.168.7.2: ICMP echo request, id
> 11873, seq 265, length 64
> 11:22:59.805624 IP 192.168.1.1 > 192.168.7.2: ICMP echo request, id
> 11873, seq 266, length 64
> 11:23:00.813283 IP 192.168.1.1 > 192.168.7.2: ICMP echo request, id
> 11873, seq 267, length 64
> 11:23:01.821354 IP 192.168.1.1 > 192.168.7.2: ICMP echo request, id
> 11873, seq 268, length 64
>
>
>  At rt-2 eth2:
>  xuanliu at rt-2:~$ sudo tcpdump -i eth2 icmp -n
> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
> listening on eth2, link-type EN10MB (Ethernet), capture size 65535 bytes
> 11:24:08.347513 IP 192.168.1.1 > 192.168.7.2: ICMP echo request, id
> 11873, seq 334, length 64
> 11:24:09.355769 IP 192.168.1.1 > 192.168.7.2: ICMP echo request, id
> 11873, seq 335, length 64
> 11:24:10.363503 IP 192.168.1.1 > 192.168.7.2: ICMP echo request, id
> 11873, seq 336, length 64
>
>  At rt-5 eth5:
>  xuanliu at rt-5:/usr/local/xorp/sbin$ sudo tcpdump -i eth5 icmp -n
> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
> listening on eth5, link-type EN10MB (Ethernet), capture size 65535 bytes
> 11:24:52.122424 IP 192.168.1.1 > 192.168.7.2: ICMP echo request, id
> 11873, seq 376, length 64
> 11:24:53.130022 IP 192.168.1.1 > 192.168.7.2: ICMP echo request, id
> 11873, seq 377, length 64
> 11:24:54.138424 IP 192.168.1.1 > 192.168.7.2: ICMP echo request, id
> 11873, seq 378, length 64
>
>  Based on the routing table at rt-5, the packet to 192.168.1.0 should be
> forwarded to link 192.168.3.0. So I checked the interface rt-5:eth3, and it
> showed nothing.
>
>  xuanliu at rt-5:/usr/local/xorp/sbin$ sudo tcpdump -i eth3 icmp -n
> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
> listening on eth3, link-type EN10MB (Ethernet), capture size 65535 bytes
>
>
>  Similarly, I couldn't ping rt-5:eth1 (192.168.13.2) from rt-1 neither.
> But I can ping 192.168.10.2, and 192.168.10.1, and the packets were
> forwarded from rt-5:eth3(192.168.3.2) to rt-5:eth2(192.168.10.2)
>
>
>  Could you please provide any suggestion on how to troubleshooting this
> problem?
>
>
>  Thanks,
>
>  -- Xuan​ Liu
>
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>
>
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