TLOC preference

[knaik99]

Preference for directing traffic to the tunnel. A higher value is preferred. When a vEdge router
has multiple tunnels (that is, multiple TLOCs), only the TLOC or TLOCs with the highest
preference are chosen using inbound path selection. However, traffic is influenced in both the
directions; inbound as well as outbound. If all TLOCs have the same preference and no policy
is applied that affects traffic flow, traffic flows are evenly distributed among the tunnels, using
ECMP. For example, when a preference of 100 on one TLOC and a preference of 50 on the
other TLOC is set, the preference chosen is the TLOC with a preference of 100.

Can anyone explain bold letter sentence about TLOC preference?

[husseino]

The statement is a bit vague, can you please site the source of this statement.

Anyway, here're some thoughts

• First, you need to understand that direction are from vSmart perspective.
• Inbound policy
  • If site 1 advertise subnet x from tloc_A and set preference to 100, and this policy is applied in the inbound direction to vSmart.
  • In bound policy will affect vSmart selection, and vSmart will choose the best route based on the applied preference.
  • vSmart will then (based on the outbound policy) reflected the best path to rest of the network.
• Outbound direction.
  • If site 1 advertise subnet x from tloc_A
  • Outbound direction policy gives you more control in this case, where you can add the route preference to the route as it is being advertised to sites.
  • In Outbound direction, you can apply policy to different site scopes. For example scope1: sites 1-100, DC1 routes with tloc_pref:100 and dc2 routers with tloc_pref: 50. Scope2: sites101-200, dc1 routes with tloc_pref:50 and dc2 routes with tloc_pref: 100.

[knaik99]

it is in Cisco documnet---

https://www.cisco.com/c/en/us/td/docs/routers/sdwan/command/sdwan-cr-book.pdf

[husseino]

This particular statement is NOT about the TLOC preference as an attribute of IP route, it is about statically configure TLOC preference under tunnel interface. This value will be used locally to choose the TLOC for outbound traffic. It will also be used for inbound tunnels.

This is the test from router 1.14.1.1 without TLOC configured, the router is using all available tunnels for outbound traffic.

After applying the configuration, the router is choosing only the TLOC with the highest preference.

Other sites will also use the same tunnel for inbound traffic.

You use this feature if you want to use circuits on active standby mode because the circuits of the highest TLOC will be used first, when they fail, circuits with lower or no preference will be used. 

Please vote if you find this answer helpful

[knaik99]

https://www.cisco.com/c/en/us/td/docs/routers/sdwan/command/sdwan-cr-book.pdf

[svemulap@cisco.com]

hi KNAIK99 -

All it means is the return traffic will also be influenced.
This is due to, node in question, when configured will advertise this preference to vSmart, which in tun will it to other nodes.
This will let remote nodes to know, to which TLOC to prefer when they send their updates to the local node.

HTH.