ping/vpn issue over ATM

linuxman25 · ‎07-07-2003

The issue that i'm having is that i'm trying to setup a VPN between two dsl customers but the two cannot ping each other. Basically i have the BVI setup with an ip address, lets say, "1.1.1.1". Business A has a Linksys DSL/VPN router with an ip address of like 1.1.1.2 and business B has an ip address of lets say 1.1.1.3 and the same model linksys DSL/VPN router. Both VPN routers have the gateway set correctly, (1.1.1.1). the subnet i'm using is a split 128 so the mask is 255.255.255.192. this is the mask on the BVI interface as well as all of the customers. here is what is very odd. Lets say you are at business A.....one can ping the default gateway (1.1.1.1) just fine and get out over the internet just fine, however one can NOT ping business B (1.1.1.3). The exact same scenerio exists at business B. This doesn't make sense either: lets say i install dsl at a residential customer's home, with an ip of 1.1.1.4 or something. he CANNOT ping either of the businesses, A or B....totally weird.

Now, here is the real kicker: Another computer on the internet, lets say a dsl customer from another service provider, can ping both business A and B just fine. Also, I can ping either business from within the cisco 2620 or on my local lan. I've been racking my brain over this for quite some time now and am about to just give up. it makes no sense and I'm not an expert on cisco's and if there could be something in the setup of it that is causing it. could it be something that is cached or something that could be causing the problem. i just don't understand how the two VPN routers can ping other stations and other stations on a different network can ping them but they cannot ping one another....GRRRRR

rlcarr · ‎07-09-2003

Sorry but this isn't totally wierd, it is normal. What you have is an NBMA (non broadcast multiple access). This means your clients don't have the ability to ARP for each other. They are not truelly on the same broadcast medium even though Layer 3 wise they *think* they're all together. They actually have just a point to point connection to the 2620.

Unfortunately, I can't think of the command to fix this. In OSPF, it was simply just the 'ip ospf network ' statement. In BGP its to static map your peer. For the DSL you will need to search Cisco on 'NBMA'

Sorry I couldn't be more helpful,

~ron

CCNP, CCDA, CNE

linuxman25 · ‎07-09-2003

thanks...I've searched on cisco's site for NBMA and there is so much stuff that comes up I'm not quite sure what i'm looking for. What is odd is that yesterday i did a DSL install at another business and i could ping BOTH of those other businesses that can't ping one another..