DHCP/multicast on SD-Access overlay network

[yu-inoue1]

Hi,

Could you please let me know about DHCP/multicast routing on SD-Access overlay network?

Can use DHCP/multicast routing on SD-Access overlay network?

case1: DHCP server and DHCP client on SD-Access overlay network

case2: DHCP client on SD-Access overlay network and DHCP server on SD-Access overlay network.

case3: multicast routing on SD-Access overlay network.

is all case possible?

[Shawn Wargo · Accepted solution]

Hello.

The DHCP server must be outside of the SD-Access fabric, either mulitple hops away (e.g. DC) or directly connected to the Fabric Border (as part of outside protocol / address space).

This means case 1 does not work. It is technically possible (advertise the DHCP server as an EID in the fabric overlay), but we have not tested this design (as most DHCP servers are outside, e.g. DC).

You can read more about DHCP in SD-Access & Campus Fabric here:

Campus Fabric Configuration Guide, Cisco IOS XE Everest 16.6.1 (Catalyst 9500 Switches) - Configure DHCP in Campus Fabr…

IPv4 Multicast routing (PIM-SM or SSM) is supported in SD-Access fabric as a LISP overlay (known as head-end replication: multicast over unicast).

You can read more about Multicast in SD-Access & Campus Fabric here:

Campus Fabric Configuration Guide, Cisco IOS XE Everest 16.6.1 (Catalyst 9500 Switches) - Campus Fabric [Support] - Cis…

Hope that helps!

[Stefan Tiefel]

Hello,

did you do any further testings on the case 1?
We have a scenario where an SDA network is deployed but we now need to "migrate" a old vlan into it with a seperate dhcp server and clients in it and nothing can be changed...

[maxime.bassière]

Hello,

when you say : "advertise the DHCP server as an EID in the fabric overlay" how do you perform this? we need to specify it at the border level lisp site-MAP? 

I try to understand how we can achieve this with by example a layer2 border. Let's say you are migrating an existing network through a l2 border, the DHCP server is in the same subnet. It would mean that the server is already know in the lisp table. How can we force the dhcp flow to go through it and not to the layer3 border?

[Farhan Mohamed]

You can read more about DHCP in SD-Access & Campus Fabric here:

Campus Fabric Configuration Guide, Cisco IOS XE Everest 16.6.1 (Catalyst 9500 Switches) - Configure DHCP in Campus Fabr…

You can read more about Multicast in SD-Access & Campus Fabric here:

Campus Fabric Configuration Guide, Cisco IOS XE Everest 16.6.1 (Catalyst 9500 Switches) - Campus Fabric [Support] - Cis…