[c-nsp] Weird ADSL bridging issue

[Karsten Thomann]

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
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