Question

For a BGP networking lab, why would there be a next hop address of 0.0.0.0 for ipv4 and :: for ipv6?

In my lab, I used show bgp ipv4 unicast neighbors and saw a next hop of 0.0.0.0, and also used show bgp ipv6 unicast neighbors and saw a next hop of ::

What would cause this to happen, and what does it mean? I haven't used any route summarization or aggregation as of yet, and haven't set any static routes with quad zero, so what does it mean? Thanks

Answer 1

In IPv4, 0.0.0.0 is a non-routable address that describes an invalid or unknown target.

However, it means something different depending on whether it's seen on a client device like a computer or on a server machine.

Personal computers and other client devices normally show an address of 0.0.0.0 when not connected to a TCP/IP network. A device might give itself this address by default whenever it is offline.

It might also be automatically assigned by DHCP in the case of address assignment failures.

When set with this address, a device cannot communicate with any other devices on that network.

In the context of routing, 0.0.0.0 usually means the default route, i.e. the route which leads to ‘the rest of’ the Internet instead of somewhere on the local network, especially for DHCPDISCOVER packets.

The above is also same for IPv6 :: .

In some cases 0.0.0.0(in IPv4) and :: (in IPv6) is set to the gateway router or compter. It connect your network with the another network or the internet.

In your lab, the next hop is 0.0.0.0(in IPv4) and :: (in IPv6), this means that hop is the gateway point of your lab which connect your lab's network to another network or the internet.