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Author Topic: Unable to Delete Null Route to my /56  (Read 10035 times)

fukawi2

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Unable to Delete Null Route to my /56
« on: December 12, 2011, 03:42:09 PM »

Hi all,

I have native IPv6 from my ISP with an assigned /56. My ISP has provided a Cisco 887 to go with it.

I've added a static route for the /56 to be routed via my firewall/gateway device (2001:44B8:4126:C600::F0), but I still seem to have a Null route above that in the Cisco config that I am unable to delete:
Code: [Select]
Natures#show ipv6 route 2001:44B8:4126:C600::/56
Routing entry for 2001:44B8:4126:C600::/56
  Known via "static", distance 1, metric 0
  Route count is 2/2, share count 0
  Routing paths:
    directly connected via Null0
      Last updated 08:30:35 ago
    2001:44B8:4126:C600::F0
      Last updated 00:10:23 ago

Natures#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Natures(config)#no ipv6 route 2001:44B8:4126:C600::/56 Null 0 
% No matching route to delete
Natures(config)#

I'm not very good with Cisco or IPv6, so can someone point out WTH I'm doing wrong? :)
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broquea

  • Sr. Network Engineer, HE.NET AS6939
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Re: Unable to Delete Null Route to my /56
« Reply #1 on: December 12, 2011, 03:59:19 PM »

what does the output of the following come back with:
Code: [Select]
sh run | i 2001:44B8:4126:C600
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fukawi2

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Re: Unable to Delete Null Route to my /56
« Reply #2 on: December 12, 2011, 04:35:25 PM »

what does the output of the following come back with:
Code: [Select]
sh run | i 2001:44B8:4126:C600
Code: [Select]
Natures#sh run | i 2001:44B8:4126:C600
ipv6 route 2001:44B8:4126:C600::/56 2001:44B8:4126:C600::F0
That means it's picking the correct route? Can you explain that command means? :)
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kcochran

  • Sr. Network Engineer, Hurricane Electric
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Re: Unable to Delete Null Route to my /56
« Reply #3 on: December 12, 2011, 07:50:57 PM »

That means it's picking the correct route? Can you explain that command means? :)
It means to pipe "show running-config" through the 'include' command, which is effectively a grep.  This is the Cisco equivalent of "cat file.cfg | grep blah"

A better way to see if something's hiding in your configuration would be to check for the null, and not the prefix.  It's possible you have something within that prefix assigned to Null0 with a /56 mask, which wouldn't necessarily be caught by the previous command.  It would be odd, but the one thing you can always rely on with networking gear, is that the odd things happen.

How about trying "sh run | i ull" which should pull all your configuration lines which reference null in any fashion.  Yes, I'm just searching for 'ull', just in case it's also going to case-match.
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fukawi2

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Re: Unable to Delete Null Route to my /56
« Reply #4 on: December 12, 2011, 08:02:10 PM »

It means to pipe "show running-config" through the 'include' command, which is effectively a grep.  This is the Cisco equivalent of "cat file.cfg | grep blah"

Nice, that makes sense. I keep forgetting you can abbreiviate IOS commands ('sh' instead of 'show'). Here I was thinking IOS had some form of bourne shell :P

How about trying "sh run | i ull" which should pull all your configuration lines which reference null in any fashion.  Yes, I'm just searching for 'ull', just in case it's also going to case-match.
It appears it's no where in running config...
Code: [Select]
Natures#sh run | i ull
Violators will be prosecuted to the fullest extent of both civil
Natures#
But....
Code: [Select]
Natures#show ipv6 route
IPv6 Routing Table - default - 8 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
       B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
       D - EIGRP, EX - EIGRP external, ND - Neighbor Discovery
       O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
S   ::/0 [1/0]
     via Dialer1, directly connected
C   2001:44B8:4030:97::/64 [0/0]
     via Dialer1, directly connected
L   2001:44B8:4030:97:CEEF:48FF:FEAF:ECB8/128 [0/0]
     via Dialer1, receive
S   2001:44B8:4126:C600::/56 [1/0]
     via Null0, directly connected
     via 2001:44B8:4126:C600::F0
C   2001:44B8:4126:C600::/64 [0/0]
     via Vlan1, directly connected
L   2001:44B8:4126:C600::1/128 [0/0]
     via Vlan1, receive
LC  2001:44B8:4126:C6FF::1/128 [0/0]
     via Dialer1, receive
L   FF00::/8 [0/0]
     via Null0, receive
Natures#

It appears to be working (ie, I've managed to get addresses from Router -> Firewall -> Desktop and I can ping in and out from my desktop.... So I guess I'm just more confused than broken.
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kcochran

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Re: Unable to Delete Null Route to my /56
« Reply #5 on: December 12, 2011, 08:14:18 PM »

Hah.  I see it now.  Probably has to do with the Dialer interface.  Null is probably there to trigger the dialer to come up if it's down and sink the traffic if it doesn't.
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fukawi2

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Re: Unable to Delete Null Route to my /56
« Reply #6 on: December 12, 2011, 08:17:49 PM »

Hah.  I see it now.  Probably has to do with the Dialer interface.  Null is probably there to trigger the dialer to come up if it's down and sink the traffic if it doesn't.
Lost me, but OK, I'll trust you :P
Thanks for your input... IPv6 is slowly getting deeper and deeper into my network ;)
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