Packets being dropper after next-hop IP not being in Neighbour Table

mattbra · ‎05-14-2023

Good afternoon,

I am working on Packet Tracer to be able to send packets from computers to each other on different vlans with IPv6, on IPv4 it works as it should, you can ping other computers and they return an echo message but with IPv6 I am not being able to do it.

The problem is that when the packet goes to the default gateway it is discarded when the packet is going out because the switch multilayer does not have in its neighbor table the mac of the destination and a NDP packet is created and sent to discover the MAC of the computer. But even though the Multilayer switch already has in its table the IP address and the mac because it has learned it already, I check this with on <show ipv6 neighbors> it still does not send it to the destination and the source computer does not get any response, I am using EtherChannel and Vlans to configure 4 multilayer switches but the current configuration works correctly with IPv4.

Has anyone had this problem? Could you tell me what could be the error?

The default gateway for the SVI of the VLANs are all on MPLS11 and MPLS11 is also the Root Bridge for PSVT.

This is the problem im facing, the packet with source from PC0 tries to send an echo message to PC1 with the corret destination IPv6 address but the packet in MPLS11 gets discarted to create an NDP message even if the destination MAC address is already added to the neighbours table.

Neighbours Table:

I have added the .pkt

Thanks,

Matt.

Flavio Miranda · ‎05-14-2023

Hi

You are missing routes on the return traffic. You have routes sending from the Layer3 to the first route and from the first route to the second. But you need to put routing on the return traffic and it need to be specific routes.

mattbra · ‎05-14-2023

Hi, but MPLS11, the Multilayer Switch has the networks directly connected because it has the svi of the vlans and it's the default gateway of them, even with this should I add manually the routes to route the return traffic?

When you say Layer3 you mean the Multilayer Switch or the OSI Layers?