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Notable Replies

  1. Hi Rene,
    Can you please explain why do neighbors need to be activated ? In the old syntax ( without address families) these was no "activate". After declaring the neighbors they were activated by default ? But in the new format they are "born" not activated so we need to activate them ?
    Thank you.

  2. Hi Adrian,

    In the "global" configuration mode of BGP we configure IPv4 unicast which is activated by default. All the other stuff like IPv6 unicast/multicast, IPv4 multicast and VPN routes are disabled by default so that's why we need to activate them. I guess it makes sense, BGP is/was mostly used for IPv4 unicast and not everyone uses all the other address families.


  3. Rene, i have a question, on your 1st config on IPv6 adjacency & IPv6 prefixes, you said that
    you disabled the ipv4 address family, so you disabled that by typing the command "no neighbor activate" under the address family IPv4?
    so by default, the IPv4 was activated?
    what will happened if you only typed...

    R1(config)#router bgp 1
    R1(config-router)#neighbor 2001:db8:0:12::2 remote-as 2
    R1(config-router)#address-family ipv6
    R1(config-router-af)#neighbor 2001:db8:0:12::2 activate
    R1(config-router-af)#network 2001:db8::1/128

    this is the 1st time i encounter this command, especially the address family, what does it really do? why do we need to enable or disable this one? as per your explanation, it only specifies "address family". How the address family affects the bgp?

    thanks! sorry for many questions.

  4. Rene,
    Hi. Great post. A couple questions.
    1. For the show command validations I noticed you were using the "show ip bgp ipv6 unicast", is the latest approach to drop the 'ip" and just issue "show bgp ipv6 unicast"? From what I could see there is no real difference in the options that one can select for this, but I did try to do a soft BGP clear and couldn't find the same comparable options (as "clear ip bgp ipv6 unicast" didn't present the option but "clear bgp ipv6 unicast" did)?
    2. So in the two examples above for the first one the MP-BGP different ASNs became neighbors by using IPv6 and then advertising IPv6 prefixes. In the second example the neighbor relationship was established using IPv4 and then sent prefixes via IPv6. I went ahead and did a simple test within my lab and was also able to establish both a IPv6 and IPv4 neighbor relationship below - I assume that would be the method required if wanted to advertise both IPv4 and IPv6 prefixes. Just looking for a sanity check.

    router bgp 200
    bgp log-neighbor-changes
    neighbor remote-as 100
    neighbor 2001:10:36:36::6 remote-as 100
    address-family ipv4
      network mask
      neighbor activate
      no neighbor 2001:10:36:36::6 activate
    address-family ipv6
      network 2001:10:33:33::/64
      neighbor 2001:10:36:36::6 activate

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