Routing & Switching Confusing Issue ?

[shakeelahmadch]

Hello All,

i am facing a strange issue, or i am unable to guess it theoraticaly. Please if someone can guide me a little :

Scnerio is, i am basically trying to limit speed of a PC. Following is the IP Addressing:

*****************************

ROUTER - CISCO 2620

IP: 202.135.143.1 MASK 255.255.255.224

202.135.143.33 MASK 255.255.255.224

ROUTE: ip route 202.135.143.40 255.255.255.224 202.135.143.35

*****************************

SPEED BLOCKER PC - LINUX

IP: 202.135.143.35/255.255.255.224

GATEWAY: ROUTER (202.135.143.33)

*****************************

CLIENT PC - WINDOWS

IP: 202.135.143.40

MASK: 255.255.255.224

GATEWAY: 202.135.143.35

*****************************

Now when client gives the gateway as normal (202.135.143.35) all speed limits works but if client change its gateway directly to 202.135.143.1 , His UPLOAD speed is out of control now, although router then route this traffic back to the 202.135.143.35 and client's DOWNLOAD speed get capped.

I am quite confuse how a different subnet IP is communicating with a different subnet IP without a router. Thing to note is that they are in a same VLAN. Can any body explain it theoratically (how is this was possible for a packet to pass to another network without a router) and solution to stop client doing it.

regards,

Shakeel Ahmad

[powellcw]

I can't say why the microsoft ip stack is allowing direct comm with 202.135.143.1.

However, a solution to you problem could lie in the fact that you have an incorrect route statement on the 2620 router. 202.135.143.40 is not a subnet address. The statement should be:

ip route 202.135.143.32 255.255.255.224 202.135.143.35

[Harold Ritter]

Try to disable the proxy arp functionality on the router interface. It should take care of it.

interface fa0/0

no ip proxy-arp

Hope this helps,

[shakeelahmadch]

Thanx powellcw@ci.durango.co.us and also Thanx hritter for replying, but both of the above answers didn't realy worked.

powellcw@ci.durango.co.us i would say , we are talking about ARP or UPLOAD speed, there'e no issue of routing problem, we can have a route /24 for routing 1 IP.

And Hritter, i tried disabling ARP Proxying, it also did'nt worked. Can you ask someone of your coleague about this issue. or any of your opinion. ?

regards,

Shakeel Ahmad

[milan.kulik]

Hi,

what is your bandwith blocker idea generally?

As I can see, all devices (router, PC, Linux blocker) are in the same subnet 202.135.143.32/27.

So if nothing special were running on the Linux machine, when IP packet comes from the PC with a destination somewhere behind the router, the Linux machine would reply with ICMP redirect to the PC, saying: "Use 202.135.143.33 next time." And PC would talk to the router (202.135.143.33, not 202.135.143.1) next time.

AFAIK, ip route 202.135.143.40 255.255.255.224 202.135.143.35 command will have no effect when all machines (202.135.143.40, 202.135.143.35 and router 202.135.143.33) are in the same subnet 202.135.143.32/27.

Hritter might be right, it could also be an proxy-arp problem. Have you cleared the arp table on your PC after proxy-arp disabling on the router?

Regards,

Milan