09-07-2010 11:26 AM
Hello all
I've recently purchased a Cisco RVS4000 router. One feature of the router which appeals to me is the jumbo frame support. In anticipation for getting jumbo frames set I began doing some testing of the router and found some curious results.
With everything set at defalts (not attempting jumbo frame) I'll ping 192.168.1.1 -f -l 1473 from a windows xp workstation and I'll get "Packet needs fragmentation but DF set". This is what I would expect. However, when I ping 192.168.1.1 -f -l 1472 I get a request timed out message, which is not what I would expect. I get request timed out messages all the way down to 1,000 something at which point the packets go through fine. I get the same behavior pinging from different computers and/or different cables. When I plug in my old router and ping 192.168.1.1 -f -l 1472 the packet goes through just fine. Again with the old router, 192.168.1.1 -f -l 1473 produces a fragmentation message.
So is the RVS4000 blocking the pings as some sort of security feature or is there something wrong with the router?
Thanks for your help.
Matt
09-09-2010 07:31 AM
I have seen some problems with this router droping sizable (even though still valid) pings.
Check the IPS log...I remember seeing something in my IPS log...something about it dropping pings.
09-11-2010 07:26 AM
The log shows a list of suspected attacks of the type UDP_SMURF from the ip address of my workstation so it looks to me that the router is blocking the pings.
Here's where this router is a bit over my head...is IPS referring to the firewall? Can I temporarily disable it for the pupose of testing frame sizes?
Thanks for your help I definately know now that I do not have a defective unit.
Matt
09-11-2010 03:19 PM
IPS is intrusion prevention system.
It's sort of like a suppliment to the firewall.
Yes, you can disable the IPS but I've heard there are many problems with doing so...
Temporarily, you should be fine to test.
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