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Gerald Combs
Asked: 2010-10-04 10:39:23 +0800 CST

How do you display the IPv6 NDISC cache in Linux?

  • 772

Suppose you've configured IPv6 proxy NDP on one of your Linux systems like so:

ip -6 neighbor add proxy 2001:db8:1234::5 dev eth1

How do you verify that the configuration took? ip -6 neighbor show doesn't appear to show proxy entries and ip -6 neighbor show proxy isn't a supported command.

linux ipv6 iproute2 ndp

3 Answers

  1. Best Answer

    I think the ip tool just doesn't print the NTF_PROXY flag. In ip/ipneigh.c, after the NTF_ROUTER block, try adding

       if (r->ndm_flags & NTF_PROXY) {
            fprintf(fp, " proxy");
    }

    I don't have an NDP proxy installation, so I can't test it. From reading the kernel sources, however, it appears that the entries will all get returned and the flag should be set for proxy entries.

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  2. have you tried ip ntable ?

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  3. For the sake of completeness:

     shell> ip -6 neigh del proxy 2001:db8:1234::1234:5678 dev eth1
 shell> ip -6 maddr show dev eth1                      
 3:      eth1
         inet6 ff02::1:ff34:5678
 ...

    It's just the last 6 nibbles but that's often all you need.

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