[c-nsp] ASR920 - new lines in config after reboot

Shawn L shawn at rmrf.us
Sun May 16 09:27:21 EDT 2021

As strange as the ASR920 routers can behave at times, I've never seen this
one before.  Wondering if anyone else has.

We have a remote site with a ASR920-12CZ router running 3.16
(03.16.05.S.155-3.S5) which has been fine for quite a while now (years).
Yesterday there was a power outage at the site and everything was out for
several hours.

Once the power situation was fixed, I went to the site and turned the UPS
back on, powered up the 920, etc.  Everything seemed to go fine -- I did
have to reboot the 920 a couple of times to get it to boot, though I've
seen that behavior before (it stalls 80% of the way through the boot, after
it displays the full cisco banner but before it starts bringing interfaces
up).  Anyway, it came back up, everything seemed fine.  I left.

This morning I noticed that our rancid installation is complaining that the
router's config changed.  Of course it did, it rebooted so times will be
different, etc.  But I also found lines inserted into each interface's

interface GigabitEthernet0/0/0
 description Site-UPS
 no ip address
 + ip broadcast-address
 negotiation auto
 service instance 1 ethernet
  encapsulation untagged
  bridge-domain 1

interface GigabitEthernet0/0/8
 description Cust: <Customer name and id>
 no ip address
 + ip broadcast-address
 media-type auto-select
 negotiation auto
 service instance 56 ethernet
  encapsulation untagged
  service-policy input 50M
  service-policy output 500M
  bridge-domain 56

interface BDI1
 description Untagged site MGT addresses
 ip address
 +ip broadcast-address

The "ip broadcast-address" has somehow been added to every interface, both
physical and bridge-domain.  In some cases it's not, it's the
subnet the interface is on -- though not really the broadcast.

In any event, I was on-site and the only one touching the box.  I certainly
didn't add them, and we don't do any ZTP or automated configuration, etc.
Also didn't change the IOS, etc.  So I'm trying to find out how it suddenly
got in there.


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