What happened to the no auto-summary command for VRF address-family?

Answered Question
Aug 27th, 2010
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So we are looking at upgrading one of our 7206VXR NPE-G1s to 12.2(33)SRD4 from 12.2(31)SB17.  We duplicated the production router in the lab running the SB(17) code.  Then we upgraded to the SRD4 code and compared the configs.  It seems the no auto-summary command has been removed from all of the address-family ipv4 vrfs.  I should point out that the default behavior is not to summarize and it isn't summarizing, but the option to enable it isn't there either.  I can't see any time when we would want to turn it on but I can't find any documentation saying when that command was removed or changed and it bothers me.  I'm still looking but thought I would throw this out there in case someone had a quick reference.  There are a lot of release notes to read.

Correct Answer by Jerry Ye about 6 years 7 months ago

The behavior has been changed in the current IOS.


"The MPLS VPN Per VRF Label feature does not support auto-summary."


http://www.cisco.com/en/US/docs/ios/iproute_bgp/command/reference/irg_bgp1.html#wp1088373


The behavior was modified under vrf address-families because, unlike aggregate-address command, auto-summarization does not install a summary route on the router where summarization is performed. This may lead to scenarios where mpls label switched paths can break. So the cli has been modified to prevent auto-summary configuration under vrf address-families and default behavior is 'no auto-summary' for vrf address-families.


The workaround is to use aggregate-address for BGP summerization under vrf address-families.


HTH,

jerry

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Giuseppe Larosa Fri, 08/27/2010 - 10:11
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Hello David,

the default setting is now no auto-summary so it is not shown in configuration


also no sync is now default


Hope to help

Giuseppe

David Williams Fri, 08/27/2010 - 11:12
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Thank you Giuseppe.  Are you aware of why they would remove the ability to turn it on vrf by vrf?  I do see that no auto-summary is the default and thus the command is removed, but it does not appear that you have the option to enable it in a vrf at all.  Note the difference in available commands below.


Thanks


SB17


Router Address Family configuration commands:

  aggregate-address    Configure BGP aggregate entries

  auto-summary         Enable automatic network number summarization

  bgp                  BGP specific commands

  default              Set a command to its defaults

  default-information  Control distribution of default information

  default-metric       Set metric of redistributed routes

  distance             Define an administrative distance

  distribute-list      Filter networks in routing updates

  exit-address-family  Exit from Address Family configuration mode

  help                 Description of the interactive help system

  maximum-paths        Forward packets over multiple paths

  neighbor             Specify a neighbor router

  network              Specify a network to announce via BGP

  no                   Negate a command or set its defaults

  redistribute         Redistribute information from another routing protocol

  synchronization      Perform IGP synchronization

  table-map            Map external entry attributes into routing table

  timers               Adjust routing timers


SRD4


Router Address Family configuration commands:

  aggregate-address    Configure BGP aggregate entries

  bgp                  BGP specific commands

  default              Set a command to its defaults

  default-information  Control distribution of default information

  default-metric       Set metric of redistributed routes

  distance             Define an administrative distance

  distribute-list      Filter networks in routing updates

  exit-address-family  Exit from Address Family configuration mode

  help                 Description of the interactive help system

  maximum-paths        Forward packets over multiple paths

  neighbor             Specify a neighbor router

  network              Specify a network to announce via BGP

  no                   Negate a command or set its defaults

  redistribute         Redistribute information from another routing protocol

  synchronization      Perform IGP synchronization

  table-map            Map external entry attributes into routing table

Peter Paluch Sat, 08/28/2010 - 00:33
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David,


Just a quick thought: the command may not be visible in the help but if you typed it exactly in the full form, i.e., auto-summary - would it be accepted or not?


Best regards,

Peter

David Williams Mon, 08/30/2010 - 08:56
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I did try that too.  Although it does take the command it doesn't seem to do anything.  As you can see in the example.  Nothing changed in the config.  There isn't any auto summarization taking place within the vrf either.  It's really not a deal breaker, I would just like an explanation as to why this was removed.  The only place I can enable auto-summary is in the ipv4 address family but it only affects the global table not the vrfs.


TESTROUTER(config)#router bgp 65001
TESTROUTER(config-router)#address-family ipv4 vrf test
TESTROUTER(config-router-af)#auto-summary
TESTROUTER(config-router-af)#end


router bgp 65001
!
address-family ipv4 vrf test
  no synchronization
  bgp redistribute-internal
  redistribute connected route-map CUSTOMER-Connected-Redistribute
  redistribute static route-map CUSTOMER-Static-Redistribute
  neighbor 172.16.1.2 remote-as 65002
  neighbor 172.16.1.2 activate
  default-information originate
exit-address-family

Correct Answer
Jerry Ye Mon, 08/30/2010 - 09:21
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The behavior has been changed in the current IOS.


"The MPLS VPN Per VRF Label feature does not support auto-summary."


http://www.cisco.com/en/US/docs/ios/iproute_bgp/command/reference/irg_bgp1.html#wp1088373


The behavior was modified under vrf address-families because, unlike aggregate-address command, auto-summarization does not install a summary route on the router where summarization is performed. This may lead to scenarios where mpls label switched paths can break. So the cli has been modified to prevent auto-summary configuration under vrf address-families and default behavior is 'no auto-summary' for vrf address-families.


The workaround is to use aggregate-address for BGP summerization under vrf address-families.


HTH,

jerry

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