if IPAddress(ip_addr_src) and IPAddress(ip_addr_dst):
    def plot_path(dot):
        def lookup_addr_routing_table(src_addr, dst_addr, routing_table):
            root = None
            seen = None

            # Find the root node.
            for route, advertisers in routing_table.items():
                if IPAddress(src_addr) in IPNetwork(route):
                    for advertiser in advertisers:
                        if advertiser.nexthopip == '':
                            root = advertiser
                if IPAddress(dst_addr) in IPNetwork(route):
                    seen = advertisers

            # Now we have found our root node, find nexthop from root node to
            # dst_addr.
            for advertiser in seen:
                if advertiser.hostname == root.hostname:
                    if advertiser.nexthopip == '':
                        return advertiser
                    else:
                        return lookup_addr_routing_table(advertiser.nexthopip, dst_addr, d)