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Part 2: Cisco SDWAN tloc extension (gre-from)

September 19, 2022 ,

Cisco SDWAN tloc extension (gre-to and gre-from)

By using a TLOC extension interface, a WAN Edge router can communicate with the adjacent WAN Edge router over the interface to use other WAN edge router ISP media. As we discuss that in our earlier article as well

Cisco Viptela SDWAN TLOC extension Part 1

We have two more things to discuss on the TLOC extension and these are "tloc-extension-gre-from" and "tloc-extension-gre-to". Here we are going to discuss on the "tloc-extension-gre-from" and will talk about "tloc-extension-gre-to" in Part 3.

tloc-extension-gre-from
First thing, It can only work on the IOS-XE model devices used for the SDWAN features. These models are Cisco ISRs and ASRs.

What does tloc-extension-gre-from does, TLOC traffic from a branch router can be channeled through an extended interface to the local WAN. You can configure it through the vManage feature template. 

Fig 1.1- Cisco Viptela SDWAN: TLOC Extension

When you configure you need to add two things here 
tloc-extension-gre-from <extended-wan-interface-ip-address> <xconnect wan-interface-name>

<extended-wan-interface-ip-address> : GRE tunnel destination IP address used for TLOC interface. You are extending the TLOC using this interface on the branch router

<xconnect wan-interface-name> : The WAN interface that you are using for extended TLOC traffic

Sample configuration

NDNA_C8300# show sdwan running-config
sdwan
 interface ge0/0.11
  encapsulation dot1q 11
  ip address 10.10.10.1/24
!
interface ge0/0.12
  encapsulation dot1q 12
  ip address 20.20.20.1/24
!
sdwan
 interface ge0/1
  ip address 10.20.30.1
  tunnel-interface
    color private 1
  !
 interface ge0/0.11
  tloc-extension-gre-from 30.30.30.1 xconnect GigabitEthernet0/1
 !
 interface ge0/0.12
  tloc-extension-gre-from 40.40.40.1 xconnect GigabitEthernet0/2
 !
 interface ge0/2
  ip address 10.20.40.1
  tunnel-interface
    color mpls
  !
 !
!

From the above example you can see that extended wan interface as ge0/0.11 and ge0/0.12 and xconnect as GigabitEthernet0/0 and GigabitEthernet0/2.