In your scenario. PC2 will do a lookup to to find out if PC1 is on the same subnet as itself (when it's trying to reply). After it does this lookup if it determines that it's on the same subnet (by looking at the address and mask) it'll send out a ARP request to resolve the layer 2 address of the other machine. If it determines that it's not on the same subnet it will not ARP for the layer 2 address and normally would send to it's default gateway. But since you don't have one defined, it won't ARP at all nor will it send to a default gateway since it doesn't have one.
Here's an addition that I recall doing in a weird situation I was working on at work. Try putting it's own address in the default gateway and see if it doesn't ARP for EVERYTHING it is trying to connect to. Tim -----Original Message----- From: Henrique Duarte [mailto:[EMAIL PROTECTED]] Sent: Tuesday, May 14, 2002 3:02 AM To: [EMAIL PROTECTED] Subject: Re: ARP problems, anyone? [7:44108] John, thanks for the feedback. So PC2 doesn't have a default gateway configured and will send a broadcast for the address of PC1. Since router B is on the same subnet and "knows" where PC1 is, shouldn't it respond as a proxy? -H ----- Original Message ----- From: "John Neiberger" To: Sent: Monday, May 13, 2002 5:13 PM Subject: Re: ARP problems, anyone? [7:44108] > Unless you're bridging, ARP doesn't function here the way I _think_ you > think it does. > > If PC2 receives an incoming ICMP echo request and it wants to generate > a response, it first compares the network portion of the destination > address to its own subnet. If you're not bridging they will be > different. In that case, PC2 will not send an ARP request for PC1, it > will simply forward the packet to the default gateway. > > Of course, at some point PC2 will send an ARP request to get the > hardware address of Router B, but it will never need to know the > hardware address of PC1. > > Now, if you're bridging then PC1 and PC2 should be on the same subnet > and neither would require a default gateway to speak to the other. > > HTH, > John > > >>> "Henrique Duarte" 5/13/02 2:50:43 PM >>> > OK Networking gurus. I hope you can help me with this easy one: > > > > e0 e1 e0 e1 > PC1-------router A----------routerB---------PC2 > > > PC1 can ping routerB (e1) > PC2 can ping routerA (e0) > > PC1 cannot ping PC2 > > > PC2 has NO default gateway (and is not supposed to have one). I've > added a > static arp entry on PC2: PC1's IP address point to routerB e1's MAC > address. Why do I need the default gateway even though I already > configured > a static arp entry on PC2? > > Thanks in advance, > > -H Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44180&t=44108 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
