[Xorp-users] FW: cannot ping one of the interfaces from an OSPF router after installing XORP
Liu, Xuan (UMKC-Student)
xuan.liu at mail.umkc.edu
Tue Aug 5 10:28:38 PDT 2014
Thank you Avinash, apparently, I can ping rt-5: eth5 and eth3 now, without doing anything. But now I cannot ping rt-4:eth2 (192.168.2.2) from rt-2. rt-4:eth2 has received the ping request from rt-2.
From the routing table at rt-4:
xuanliu at rt-4:~$ ip route show
default via 172.16.0.1 dev eth0
172.16.0.0/12 dev eth0 proto kernel scope link src 172.17.2.8
192.168.1.0/24 via 192.168.2.1 dev eth2 proto xorp metric 20 notify
192.168.2.0/24 dev eth2 proto kernel scope link src 192.168.2.2
192.168.3.0/24 via 192.168.13.2 dev eth3 proto xorp metric 20 notify
192.168.6.0/24 via 192.168.2.1 dev eth2 proto xorp metric 30 notify
192.168.7.0/24 via 192.168.13.2 dev eth3 proto xorp metric 20 notify
192.168.10.0/24 via 192.168.13.2 dev eth3 proto xorp metric 20 notify
192.168.13.0/24 dev eth3 proto kernel scope link src 192.168.13.1
The ARP cache on rt-4 shows
xuanliu at rt-4:~$ arp -n
Address HWtype HWaddress Flags Mask Iface
172.16.0.3 ether fe:ff:ff:ff:ff:ff C eth0
192.168.2.1 ether 02:18:08:46:10:53 C eth2
172.16.0.1 ether fe:ff:ff:ff:ff:ff C eth0
There is no resolution for 192.168.13.2, which is the return path for the ping reply, according to the routing table.
However, the ARP cache keeps changing, and now it shows the all the interfaces, and the ping works.
xuanliu at rt-4:~$ arp -n
Address HWtype HWaddress Flags Mask Iface
192.168.13.2 ether 02:41:88:70:16:d2 C eth3
192.168.2.1 ether 02:18:08:46:10:53 C eth2
172.16.0.1 ether fe:ff:ff:ff:ff:ff C eth0
Thanks,
-- Xuan
________________________________
From: Avinash Sridharan <avinash.sridharan at gmail.com>
Sent: Tuesday, August 5, 2014 11:01 AM
To: Liu, Xuan (UMKC-Student)
Cc: xorp-users at xorp.org
Subject: Re: [Xorp-users] cannot ping one of the interfaces from an OSPF router after installing XORP
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<mailto: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<http://192.168.6.0/24> [ospf(110)/20]
> to 192.168.1.2 via eth4/eth4
192.168.7.0/24<http://192.168.7.0/24> [ospf(110)/20]
> to 192.168.1.2 via eth4/eth4
192.168.10.0/24<http://192.168.10.0/24> [ospf(110)/20]
> to 192.168.3.2 via eth3/eth3
192.168.13.0/24<http://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<http://192.168.1.0/24> [ospf(110)/20]
> to 192.168.3.1 via eth3/eth3
192.168.2.0/24<http://192.168.2.0/24> [ospf(110)/20]
> to 192.168.3.1 via eth3/eth3
192.168.6.0/24<http://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<http://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<http://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<http://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<http://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<http://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<http://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<http://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<http://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<http://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<http://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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