RE: question about proxy-arp [7:71113]
henry bb wrote: > > today I already know why 2500 can ping 88.1.77.1 because It doesn't make sense that the 2500 can ping all the way to the 3550 Ethernet interface based on the minimal information that you told us before. You must be doing routing. It has nothing to do with Proxy ARP, though. Maybe you have on-demand routing or something. > proxy-arp doesn't function on serial interface. > so what's the real function of proxy-arp on serial interface ? Proxy ARP has no meaning on a serial interface. ARP has no meaning on a serial interface, (unless you're referring to Frame Relay's Inverse ARP, which is a different story. It finds the IP address when the DLCI is known.) Serial interfaces don't have MAC addresses. They don't connect devices that have MAC addresses. ARP finds the MAC address when the IP address is known. It's meaningless on a serial interface. If you configure Proxy ARP on an Ethernet interface, the router could respond to ARP requests on its Ethernet side on behalf of devices on its other side, (across the serial link in this case), assuming the router knows that it can get to those devices. That's the definition of Proxy ARP. > Does it work when bridge on the serial interface ? > If bridge on serial interface,how ios transfer arp ? I think > there isn't mac address on serial interface . Is there some > encapusation to packet the mac and transfer the lan frame > through serial interface ? If you were doing bridging, then the router interfaces would be passing all broadcasts, without any knowledge of what they were passing. So Ethernet devices could theoretically ARP through a bridged network that included WAN links. The encapsulation would be whatever was configured for the WAN links. It wouldn't matter. Bridging is transparent. I've never heard of anyone doing that and there might be some gotchas, but I think it would work. The ARP data has enough info in it for it to work. It doesn't care about the data-link-layer header that is used to transfer the request or reply. Priscilla > > regards > Henry Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71154&t=71113 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: question about proxy-arp [7:71113]
Priscilla Oppenheimer wrote: > > henry bb wrote: > > > > today I already know why 2500 can ping 88.1.77.1 because > > It doesn't make sense that the 2500 can ping all the way to the > 3550 Ethernet interface based on the minimal information that > you told us before. You must be doing routing. It has nothing > to do with Proxy ARP, though. Maybe you have on-demand routing > or something. Ignore that part of the message. I just noticed the inconsistent subnet masks. Of course, it works. The router in the middle knows how to get to each subnet using the /24 mask. The router on the left knows that all of the larger subnet is out its serial interface. It's a bug to have the two routers on the left using a different subnet mask to refer to the WAN subnet, by the way. Why worry about whether it works and how it works at all if you're using a buggy configuraton? :-) Priscilla > > > proxy-arp doesn't function on serial interface. > > so what's the real function of proxy-arp on serial interface > ? > > Proxy ARP has no meaning on a serial interface. ARP has no > meaning on a serial interface, (unless you're referring to > Frame Relay's Inverse ARP, which is a different story. It finds > the IP address when the DLCI is known.) > > Serial interfaces don't have MAC addresses. They don't connect > devices that have MAC addresses. ARP finds the MAC address when > the IP address is known. It's meaningless on a serial interface. > > If you configure Proxy ARP on an Ethernet interface, the router > could respond to ARP requests on its Ethernet side on behalf of > devices on its other side, (across the serial link in this > case), assuming the router knows that it can get to those > devices. That's the definition of Proxy ARP. > > > Does it work when bridge on the serial interface ? > > If bridge on serial interface,how ios transfer arp ? I think > > there isn't mac address on serial interface . Is there some > > encapusation to packet the mac and transfer the lan frame > > through serial interface ? > > If you were doing bridging, then the router interfaces would be > passing all broadcasts, without any knowledge of what they were > passing. So Ethernet devices could theoretically ARP through a > bridged network that included WAN links. The encapsulation > would be whatever was configured for the WAN links. It wouldn't > matter. Bridging is transparent. > > I've never heard of anyone doing that and there might be some > gotchas, but I think it would work. The ARP data has enough > info in it for it to work. It doesn't care about the > data-link-layer header that is used to transfer the request or > reply. > > Priscilla > > > > > regards > > Henry > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71155&t=71113 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: question about proxy-arp [7:71113]
arp cannot pass through serial links and when u want to ask for arp router behind that serial link then u set proxy-arp on ethernet and that router reply instead router behind serial,as far as i know Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71141&t=71113 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: question about proxy-arp [7:71113]
arp cannot pass through serial links and when u want to ask for arp router behind that serial link then u set proxy-arp on ethernet and that router reply instead router behind serial,as far as i know Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71131&t=71113 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: question about proxy-arp [7:71113]
today I already know why 2500 can ping 88.1.77.1 because proxy-arp doesn't function on serial interface. so what's the real function of proxy-arp on serial interface ? Does it work when bridge on the serial interface ? If bridge on serial interface,how ios transfer arp ? I think there isn't mac address on serial interface . Is there some encapusation to packet the mac and transfer the lan frame through serial interface ? regards Henry Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71120&t=71113 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: question about proxy-arp [7:71113]
This seems to be quite obvious to me. If the packet is generated from the 2500 router , it knows that 88.1.0.0/16 is on serial 0 (directly connected). The packet reaches 2611 which has 88.1.77.1 directly conected. The return packet can also flow as 88.1.201.1 is directly conected. But this is true only if the source of the packet is 88.1.201.1 (s0 of 2500). This is bcoz any other source will not be known to 2611 and the return packet will fail. Chirag Arora > Senior System integration engineer > -Original Message- From: henry bb [mailto:[EMAIL PROTECTED] Sent: Monday, June 23, 2003 8:51 AM To: [EMAIL PROTECTED] Subject: question about proxy-arp [7:71113] 2500-s0-88.1.201.1/16--88.1.201.2/24-s1/0--2611--e0/0--88.1.77.2/24---88.1.77.1/24-f0/42-3550 I can ping from router 2500 to 88.1.77.1 even if I disable proxy-arp of 2611's s1/0. There isn't any dynamic or static routing except a default route on 3550 to 2611. I can't understand this. Does I misunderstand the function of proxy-arp ? another related question, what's the real function of proxy-arp on serial interface ? thanks! Regards Henry DISCLAIMER: Information contained and transmitted by this E-MAIL is proprietary to Wipro Limited and is intended for use only by the individual or entity to which it is addressed, and may contain information that is privileged, confidential or exempt from disclosure under applicable law. If this is a forwarded message, the content of this E-MAIL may not have been sent with the authority of the Company. If you are not the intended recipient, an agent of the intended recipient or a person responsible for delivering the information to the named recipient, you are notified that any use, distribution, transmission, printing, copying or dissemination of this information in any way or in any manner is strictly prohibited. If you have received this communication in error, please delete this mail & notify us immediately at [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71114&t=71113 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
