DNS, BGP, IPv6 and more!

Ease out your IPv6 gateway!

One of very cool features of IPv6 is link-local address which stays local to a given link. For this fe80::/10 is reserved. A /10 is a huge amount of address space in IPv6 (and in IPv4 too :) ). This means from fe80:0000:0000:0000:0000:0000:0000:0000 to
febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff.

 

Since by design link-local address stays local, the address configured on the upstream/gateway router can be kept same for ease of use and comfort. This wasn’t the case of IPv4 where each VLAN/layer 2 domain had it’s own gateway.

 

So e.g if you have two VLANs or interfaces say: Gi1/0 and Gi2/0. You decide to use 10.100.100.0/30 on Gi1/0 and 10.100.100.4/30 on Gi2/0. Thus usual configuration in IPv4 world goes as:

 

Link 1
10.100.100.1 – Uplink/gateway router
10.100.100.2 – User/downstream device

 

Link 2
10.100.100.5 – Uplink/gateway router
10.100.100.6 – User/downstream device

 

Thus link 1 user has to use gateway different from link 2 user.

 

Traditional IPv4 networking

 

IPv4 network setup

 

 

In case of IPv6 since each interface has unique global address as well as link local address, we can give any cool/easy-to-remember link local like fe80::1 on multiple interfaces and hence gateway can remain same across multiple end machines.

Say we have got a pool:  2a04:ec40:e01a::/48. Now we grab two /64 slices out of it (for each interface) –  2a04:ec40:e01a:100::/64 and 2a04:ec40:e01a:200::/64.

Link 1
2a04:ec40:e01a:100::1 – Uplink/gateway router
2a04:ec40:e01a:100::2 – User/downstream device

Link 2
2a04:ec40:e01a:200::1 – Uplink/gateway router
2a04:ec40:e01a:100::2 – User/downstream device

 

 

IPv6 networking

 

Link Local IPv6

 

 

 

Config of GW

 

User 1

 

User 2

 

 

Quick connectivity tests

 

Example of a Linux interface config file (assuming user 1 is a Linux server)

 

 

I hope you enjoyed it. With hope to see more IPv6, time for me to get some sleep! :)

SANOG 26 – Mumbai

Out in Mumbai to attend SANOG 26.

 

Meet and greet if you are attending as well or around in Mumbai. :)

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