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  • 1.  IPv4-mapped address

    Posted 10-07-2022 23:38
    Juniper training material has the following:
    If an IPv4-mapped IPv6 address is used as the BGP next hop, this means that this address must be reachable for the learned prefixes to be accepted. An ASBR, by default, will not accept a next-hop which is not directly connected.
    We also must enable V4 mapped packet processing in Junos.

    I have two routers configured as follows without "set system allow‐v4mapped‐packets " configured. But IPv6 address is reachable. What did I miss here ?
    R2
    set interfaces lo0 unit 62 family inet6 address 2011:192:220:102::1/64
    set interfaces ge-0/0/4 unit 66 family inet address 10.220.102.1/31
    set interfaces ge-0/0/4 unit 66 family inet6 address ::ffff:10.220.102.1/127
    
    set routing-instances R2 instance-type virtual-router
    set routing-instances R2 interface ge-0/0/4.66
    set routing-instances R2 interface lo0.62
    set routing-instances R2 protocols bgp group to->R5 family inet unicast
    set routing-instances R2 protocols bgp group to->R5 family inet6 unicast
    set routing-instances R2 protocols bgp group to->R5 export to->R5
    set routing-instances R2 protocols bgp group to->R5 local-as 65102
    set routing-instances R2 protocols bgp group to->R5 neighbor 10.220.102.0 peer-as 65001
    
    set policy-options policy-statement to->R5 term 1 from rib Internet2.inet6.0
    set policy-options policy-statement to->R5 term 1 from interface lo0.62
    set policy-options policy-statement to->R5 term 1 then accept
    
    root@R2# show | display set | match allow-v4mapped-packets
    
    [edit]
    
    R5
    set interfaces lo0 unit 0 family inet6 address 2011:192:221:102::1/64
    set interfaces ge-0/0/4 unit 66 family inet address 10.220.102.0/31
    set interfaces ge-0/0/4 unit 66 family inet6 address ::ffff:10.220.102.0/127
    
    set protocols bgp group to->R2 type external
    set protocols bgp group to->R2 family inet unicast
    set protocols bgp group to->R2 family inet6 unicast
    set protocols bgp group to->R2 export to->R2
    set protocols bgp group to->R2 neighbor 10.220.102.1 peer-as 65102
    
    set policy-options policy-statement to->R2 term 1 from rib inet6.0
    set policy-options policy-statement to->R2 term 1 from route-filter 2011:192:221:102::/64 exact
    set policy-options policy-statement to->R2 term 1 then accept
    
    root@R5# show | display set | match allow-v4mapped-packets
    
    [edit]
    
    root@R2# ...02::1 routing-instance Internet2 source 2011:192:220:102::1
    PING6(56=40+8+8 bytes) 2011:192:220:102::1 --> 2011:192:221:102::1
    16 bytes from 2011:192:221:102::1, icmp_seq=0 hlim=64 time=6.859 ms
    16 bytes from 2011:192:221:102::1, icmp_seq=1 hlim=64 time=6.958 ms
    
    
    
    
    
    
    ​

    thanks so much !!


  • 2.  RE: IPv4-mapped address

    Posted 10-08-2022 00:03
    The routing shows as follows:
    root@R5# run show route 2011:192:220:102::1
    
    inet6.0: 30 destinations, 38 routes (30 active, 0 holddown, 0 hidden)
    + = Active Route, - = Last Active, * = Both
    
    2011:192:220:102::/64
                       *[BGP/170] 03:22:57, localpref 100, from 10.220.102.1
                          AS path: 65102 I, validation-state: unverified
                        > to ::ffff:10.220.102.1 via ge-0/0/4.66
    ​

    The packets captured is as follows


    Should I see the IPv4 or IPv6 on the wire ?

    thanks !!