Black Hole Router?

[5uper5aiyan]

I am by no means a router/network guru so I am posting this here hoping someone can help me. I have a Nortel ARN Router connecting to multiple Nortel ARN Routers over a Frame Relay. All of my sites are fine except for 2 that are both going through a off net 3rd party. When I try to ping <ip address> -f -l 1472 it returns &quot;request timed out&quot;. When I try to ping <ip address> -f -l 1473 it returns &quot;packet needs to be fragmented but DF set&quot;. When I try to ping <ip address> -f -l 1018 it returns &quot;reply from <ip address>&quot;. I don't want to lower my MTU on my host interface because that would screw up the rest of my network. And I'm not sure how to check to make sure it's not my routers. Is there a way to only send 1018 size MTU down just these routes and leave the other routes alone? Probably not but I thought I'd ask.

Also, what can I tell my 3rd party to check without sounding like an idiot.

Any help would be greatly appreciated. Thanks in advance.

 

[tschouten]

Looks like you are using HPING or something like it? Try running a ping from the Router itself (unless that was running from the router). Just curious as to the response you get from the router itself.

I'm not familiar with Nortel routers and their commands. But the Frame-Relay is saying the Do Not Fragment Bit is set. This could be a setting on your router or it could be a setting your service providers switches.

 

[5uper5aiyan]

So should the Do Not Fragment Bit be set or should it NOT be set? When I ping from the my router it does the same thing. It will respond with a packet size of 1018 but of 1472. Both locations do the same thing.

The reason I need this working is because we only use two programs at our remote locations. A UNIX app and Citrix. The UNIX app works fine but Citrix doesn't. I'm thinking it's not working because of this.

 

[tschouten]

I would love to say no it shouldn't be set, but again, I know nothing about Nortel Routers. My guess, though, is that the do not fragment is set at the service providers side. You could call and ask them, who was working on your routers in the first place?

I would say if you can, go into the routers that do work and see if you can notice anything in their settings that is different.