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

Tue Aug 5 15:05:42 PDT 2014

Okay, I just figured it out. I needs to turn off the reverse path filtering on my VM, by default it's 1.

sudo sysctl -w net.ipv4.conf.all.rp_filter=0

sudo sysctl -w net.ipv4.conf.default.rp_filter=0

I also did similar thing to all other interfaces (eth1, eth2, ...)

Here is a bug report about this issue for ubuntu server 10.04 that has Quagga installed.

https://bugs.launchpad.net/ubuntu/+source/quagga/+bug/625812

Thank you for all the helps

?
-- Xuan

________________________________
From: xorp-users-bounces at xorp.org <xorp-users-bounces at xorp.org> on behalf of Liu, Xuan (UMKC-Student) <xuan.liu at mail.umkc.edu>
Sent: Tuesday, August 5, 2014 1:16 PM
To: Avinash Sridharan
Cc: xorp-users at xorp.org
Subject: Re: [Xorp-users] FW: cannot ping one of the interfaces from an OSPF router after installing XORP

?

It says 60 for all interfaces. I think this value is fine.

I have another setup with the same configuration, where I installed XORP 1.7 on virtual nodes on Fedora systems running Vservers.

With this setup, I don't see any problem, and I notice that the entry was added to the ARP cache on nodeA as soon as I triggered the ping from NodeB to nodeA. I checked the ARP cache timeout and it's 60 as well.

For my current setup, I'm running XORP 1.8.5 on VMs created from XEN, and each VM has Ubuntu 12.04.

I did some other test, which I'm not sure if it makes sense. I disabled the interface that was supposed to send out the reply, and enabled it immediately after disabling it,

then the ping could went through, and the ping packet was sent out from the interface which was just restarted. But by doing this, the routing table can be changed as well, so maybe it doesn't explain anything.

?

Thanks,

-- Xuan

________________________________
From: Avinash Sridharan <avinash.sridharan at gmail.com>
Sent: Tuesday, August 5, 2014 12:45 PM
To: Liu, Xuan (UMKC-Student)
Cc: xorp-users at xorp.org
Subject: Re: [Xorp-users] FW: cannot ping one of the interfaces from an OSPF router after installing XORP

May be the arp-cache timeout is too low? You can check the timeout value /proc/sys/net/ipv4/neigh/eth0/gc_stale_time here. If its too low see if changing it to larger value helps.

On Tue, Aug 5, 2014 at 10:28 AM, Liu, Xuan (UMKC-Student) <xuan.liu at mail.umkc.edu<mailto:xuan.liu at mail.umkc.edu>> wrote:

?

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<http://172.16.0.0/12> dev eth0  proto kernel  scope link  src 172.17.2.8
192.168.1.0/24<http://192.168.1.0/24> via 192.168.2.1 dev eth2  proto xorp  metric 20 notify
192.168.2.0/24<http://192.168.2.0/24> dev eth2  proto kernel  scope link  src 192.168.2.2
192.168.3.0/24<http://192.168.3.0/24> via 192.168.13.2 dev eth3  proto xorp  metric 20 notify
192.168.6.0/24<http://192.168.6.0/24> via 192.168.2.1 dev eth2  proto xorp  metric 30 notify
192.168.7.0/24<http://192.168.7.0/24> via 192.168.13.2 dev eth3  proto xorp  metric 20 notify
192.168.10.0/24<http://192.168.10.0/24> via 192.168.13.2 dev eth3  proto xorp  metric 20 notify
192.168.13.0/24<http://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?

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