Did you get a chance to take a look at the IP configuration of your DHCP clients? Router A could have been sending out proxy ARP's (like you already mentioned) and possibly ICMP redirects to your workstations.
Without the default route, and with the wrong subnet mask, the A router's routing table looks like this: C 10.67.2.0/24 S 10.67.1.0/24 Without the default route, the A router doesn't have routes for 10.67.7.x or 10.67.8.x. If the A router is replying when your workstations ARP for your servers, then your workstations are sending out packets with a destination IP address of your server, but with a destination MAC of the A router's ethernet interface. The A router has routes to your servers, so there's no problem there, except of course for inefficiency. When your servers send replies back to router A however, the router has no route back to your workstations. It did when the default route was in place, but without it the A router has no return path. That sounds far fetched, but I can't think of another explanation that fits your description of the problem. If you find yourself in such a situation again, fire up a protocol analyzer and compare destination MACs with destination IP addresses, and you'll get a better picture of what's going on. hth, Hal -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: Monday, March 18, 2002 7:42 PM To: [EMAIL PROTECTED] Subject: Appreciate Your Expertise On This Strange ARP Problem [7:38738] Hi there This is my first time to post a question. Here is a real scenario which happened a few days ago. Though the problem has been resolved, i still cannot understand what the cause is. Customer A has a partner connection to B's network. due to lack of capability on B's Router/Firewall, one of A's router is plugged directly onto B's internal LAN(sounds silly, but it is true). B's LAN use 10.67.0.0/16 address, of which 10.67.1.x is for servers, 10.67.2.x for routers/switches, 10.67.7.x and 10.67.8.x for DHCP clients. B's router has 10.67.2.1 addr. A's router on B's LAN gets assigned an ip addr 10.67.2.2,but a wrong /24 mask was given by B. since A's users need to talk to B's server, a static route(ip route 10.67.1.0 255.255.255.0 10.67.2.1) was added. A default route is also configured(ip route 0.0.0.0 0.0.0.0 10.67.2.1) on the A's router. when this default route was taken off(no obvious reason to point a default route to B's default router), all B's dhcp clients cannot talk to their own servers(10.67.1.x) any more even they are on the same subnet. B's network support was called in, and they found that the A's router is incorrectly answering ARP requests(by default ip proxy-arp is enabled on the LAN interface). and somehow the arp respone reaches the client before the server's, so the client cannot talk to the servers. the problem later was resolved by rectifying the subnet mask on A's router. but i still cannot figure out what went wrong when the default route on A's router was removed. I'll be much appreciated if anyone can shed some lights on this. regards Alec Shi Senior Support Engineer Axon Computertime Auckland NZ -- The information contained in this e-mail message is intended only for the use of the person or entity to whom it is addressed and may contain information that is CONFIDENTIAL and may be exempt from disclosure under applicable laws. If you read this message and are not the addressee you are notified that use, dissemination, distribution, or reproduction of this message is prohibited. If you have received this message in error, please notify us immediately and delete the original message. You should scan this message and any attached files for viruses. Axon Computertime accepts no liability for any loss caused either directly or indirectly by a virus arising from the use of this message or any attached file. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=38778&t=38778 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
