Wired Intelligent Edge

I'm working through a new design and have come across the L2/L3 mtu configurations on CX switches...  https://www.arubanetworks.com/techdocs/VSG/docs/020-campus-deploy/esp-campus-deploy-050-wired-core/

I've noticed that the ESP wired core design only has ip mtu 9198 set on the p2p interface to the aggregation.

interface 1/1/1 
  description CORE_TO_AGG1
  no shutdown
  ip mtu 9198
  ip address 172.18.103.2/30
  no ip ospf passive
  ip ospf network point-to-point
  ip ospf 1 area 0
  ip pim-sparse enable

But further down in the design, the Internet Connectivity Aggregation has both L2 and L3 mtu's set.

interface 1/3/11
    description RSVCP-INET
    no shutdown
    mtu 9198
    routing
    ip mtu 9000
    ip address 192.168.8.9/31
    ip ospf 1 area 0.0.0.0
    no ip ospf passive
    ip ospf network point-to-point

Why does the Core to Agg connection not have the L3 and L2 MTUs set?  If I only set the ip mtu how is it not fragmented with a L2 mtu of a default 1500?

Thanks

That's my question as well... 

Original Message:
Sent: Jan 23, 2024 03:31 AM
From: Ava Gomes
Subject: Campus Core CX uplink mtu setting, L2 and L3 or just L3?

For the Campus Core CX uplink MTU setting, is it necessary to configure it for both Layer 2 (L2) and Layer 3 (L3), or is it sufficient to configure it only for Layer 3? Share your insights on whether both layers need MTU settings or if L3 alone is appropriate.

IP MTU controls the size of IP packet for routing. you can set it on SVI or routed only port (ROP) 

The MTU at layer 2 is about the size of Ethernet frame.

generally for a CX switch ROP, I would set both ip mtu and mtu to be the same 9198.

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Any opinions expressed here are solely my own and not necessarily that of HPE or Aruba.
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Original Message:
Sent: Jan 24, 2024 09:08 AM
From: victorcastro
Subject: Campus Core CX uplink mtu setting, L2 and L3 or just L3?

That's my question as well... 

Original Message:
Sent: Jan 23, 2024 03:31 AM
From: Ava Gomes
Subject: Campus Core CX uplink mtu setting, L2 and L3 or just L3?

For the Campus Core CX uplink MTU setting, is it necessary to configure it for both Layer 2 (L2) and Layer 3 (L3), or is it sufficient to configure it only for Layer 3? Share your insights on whether both layers need MTU settings or if L3 alone is appropriate.