Re: Weird routing problem. (I think)

[Ramin Dousti <ramin@cannon.eng.us.uu.net>]

It's most probably ICMP redirect from your firewall to the clients since
the firewall receives the packets and send them out of the same interface.

Try turning that off on the firewall.

echo 0 > /proc/sys/net/ipv4/conf/all/send_redirects
echo 0 > /proc/sys/net/ipv4/conf/default/send_redirects
echo 0 > /proc/sys/net/ipv4/conf/eth1/send_redirects

Ramin

On Thu, Nov 06, 2003 at 04:21:18PM +0200, Stephan Viljoen wrote:

> Hi There,
> 
> I'm sorry if I've mailed this to the wrong mailing list , but I reckon
> you guys would know best :)
> 
> Some off my clients started complaining that they're having problems
> connecting to my mail server. Now all this worked fine up until
> yesterday. I'm not blocking any ports nor am I blocking ICMP on the
> network.
> 
> If I try and ping the mail server from the clients computer I get the
> following message.
> 
> [root@ceda root]# ping 217.10.176.138
> PING 217.10.176.138 (217.10.176.138) 56(84) bytes of data.
> >From 10.0.5.1: icmp_seq=2 Redirect Host(New nexthop: 217.10.176.138) 
> >From 10.0.5.1: icmp_seq=3 Redirect Host(New nexthop: 217.10.176.138)
> 
> And here comes the weird part, the moment I restart the client's network
> all problems disappear for at least an hour or two. I have about 50
> customers on my network and only about half off them is experiencing
> this problem and it's on both Windows / linux boxes.
> 
> I only have this problem accessing the mail server, the rest of the
> servers hosted on the 217.10.176.136/29 network works fine. I can also
> ping the same clients pc from the mail server without any problems.
> 
> [root@mail routers]# ping 10.0.5.2
> PING 10.0.5.2 (10.0.5.2) 56(84) bytes of data.
> 64 bytes from 10.0.5.2: icmp_seq=1 ttl=64 time=0.260 ms
> 64 bytes from 10.0.5.2: icmp_seq=2 ttl=64 time=0.235 ms
> 
> Here's my network layout.
> 
> Cisco Router 	 : (217.10.176.149/255.255.255.252)
> 
> 		-----------------------------
> 
> FIREWALL	 : eth0 (217.10.176.150/255.255.255.252)
> 		 : eth1:client1 (10.0.5.1/255.255.255.252)
> 		 : eth1:client2 (10.0.4.1/255.255.255.252)
> 		 : eth1:mail (217.10.176.137/255.255.255.248)
> 
> Routing table for the firewall.
> 10.0.5.0	    0.0.0.0		 255.255.255.252  U  0	 0
> 0 eth1
> 10.0.4.0	    0.0.0.0		 255.255.255.252  U  0 0 0 eth1
> 217.10.176.136  0.0.0.0        255.255.255.248  U  0 0 0 eth1
> 127.0.0.0       0.0.0.0        255.0.0.0        U  0 0 0 lo
> 0.0.0.0         217.10.176.149 0.0.0.0          UG 0 0 0 eth0
> 
> 		-----------------------------
> 
> MAIL SERVER	 : eth0 (217.10.176.138/255.255.255.248)
> Routing table on the Mail Server
> 217.10.176.136  0.0.0.0         255.255.255.248 U  0 0 0 eth0
> 127.0.0.0       0.0.0.0         255.0.0.0       U  0 0 0 lo
> 0.0.0.0         217.10.176.137  0.0.0.0         UG 0 0 0 eth0
> 
> 		-----------------------------
> 
> Client PC 1 	 : eth0 (10.0.5.2/255.255.255.252)
> 
> 		-----------------------------
> 
> Client PC 2 	 : eth0 (10.0.4.2/255.255.255.252)
> 
> 		-----------------------------
> 
> Some input would be greatly appreciated.
> 
> Kind Regards
> Stephan
>