[c-nsp] Weird ADSL bridging issue

[chris]

I added "no ip proxy-arp" under BVI1 and rebooted the router to clear all
the entries in the arp table and right away as soon as the circuit came up
and i logged in I'm still seeing the same random MAC's and alot of them
even though its only up a few minutes.

To keep email from getting too long I've posted debug info here:
http://pastebin.com/AxMB3mw8



On Fri, Dec 12, 2014 at 11:29 AM, Karsten Thomann <karsten_thomann at linfre.de
> wrote:
>
> Hi Chris
>
> Is there any configured default route on the router?
> Is it possible to post output of sh ip route?
> This looks like a default route without next hop ip and proxy arp at the
> provider...
>
> Kind regards
> Karsten
>
> Gesendet von meinem BlackBerry
>   Originalnachricht
> Von: chris
> Gesendet: Freitag, 12. Dezember 2014 17:21
> An: cisco-nsp at pu ck.nether.net
> Betreff: [c-nsp] Weird ADSL bridging issue
>
> Hello,
>
> We have a small site we inherited that is still on ADSL on legacy sprint in
> the northeast.
> The ILEC is using aal5snap and we have a WIC-1ADSL with a physical ATM
> interface thats bridged to BVI1, and we get a dynamic WAN ip from the ILEC
> via DHCP on BVI1.
>
> the ADSL part of our config looks like this:
>
> *bridge irb*
> *!*
>
> *interface ATM0/0*
> * description DSL Layer2*
> * no ip address*
> * atm restart timer 300*
> * no atm ilmi-keepalive*
> * dsl operating-mode auto *
> * clock rate aal5 7000000*
> * clock rate aal2 7000000*
> * bridge-group 1*
> * bridge-group 1 spanning-disabled*
> * hold-queue 224 in*
> * pvc 8/35 *
> * encapsulation aal5snap*
> * !*
> *!*
>
> *interface BVI1*
> * ip address dhcp*
> * ip nat outside*
>
> I was looking internet into a report of weird internet issues and I found
> the arp table for BVI1 is full (several pages) of lots of random internet
> IP's with the same MAC address which isnt local to the router:
>
> *Protocol Address Age (min) Hardware Addr Type Interface*
> *Internet 17.110.228.155 26 0030.881b.f475 ARPA BVI1*
> *Internet 8.8.8.8 162 0030.881b.f475 ARPA BVI1*
> *Internet 23.3.13.24 25 0030.881b.f475 ARPA BVI1*
> *Internet 17.110.228.154 84 0030.881b.f475 ARPA BVI1*
> *Internet 74.209.254.102 24 0030.881b.f475 ARPA BVI1*
> *Internet 74.125.228.215 29 0030.881b.f475 ARPA BVI1*
> *Internet 173.194.121.18 29 0030.881b.f475 ARPA BVI1*
> *Internet 17.110.228.159 84 0030.881b.f475 ARPA BVI1*
> *Internet 69.172.216.55 24 0030.881b.f475 ARPA BVI1*
> *Internet 4.2.2.2 162 0030.881b.f475 ARPA BVI1*
> *Internet 31.13.69.80 25 0030.881b.f475 ARPA BVI1*
> *Internet 173.194.121.17 26 0030.881b.f475 ARPA BVI1*
> *Internet 17.110.224.152 36 0030.881b.f475 ARPA BVI1*
> *Internet 66.196.81.223 2 0030.881b.f475 ARPA BVI1*
> *Internet 74.125.228.219 21 0030.881b.f475 ARPA BVI1*
> *Internet 17.167.146.44 22 0030.881b.f475 ARPA BVI1*
> *Internet 173.194.121.30 26 0030.881b.f475 ARPA BVI1*
> *Internet 17.172.239.90 35 0030.881b.f475 ARPA BVI1*
> *Internet 74.122.189.133 97 0030.881b.f475 ARPA BVI1*
> *Internet 173.252.79.23 49 0030.881b.f475 ARPA BVI1*
> *Internet 17.173.255.74 144 0030.881b.f475 ARPA BVI1*
>
> Interestingly enough when I look up the OUI of that MAC I see Sierra
> Systems aka Redback which I happen to know is the DSLAM that the ILEC is
> using.
>
> Anyone seen anything like this? I am trying to figure out if its an issue
> with the bridging on the local router or telco misconfiguration.
>
> I rarely touch any ATM anymore so I'm scratching my head here but hoping
> something obvious might stand out to someone.
>
> TIA,
> chris
> _______________________________________________
> cisco-nsp mailing list cisco-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>