RD vs RT in MPLS: Route Distinguisher and Route Target

RD VS RT

Route Distinguisher (RD)

A Route Distinguisher (RD) separates routes (one VRF for each customer routing table) of one customer from another. RD is prepended to each route (64-bit identifier is prepended) within a VRF to identify which VPN the route belongs to. An RD is carried along with a route via MP-BGP when exchanging VPN routes with other PE routers.

Route Target (RT)

Route Target is a 64-bit identifier used as part of MP-BGP attribute (extended community) to identify which route should be exported or imported to specific VPN. Whereas route distinguishers are used to maintain uniqueness among identical routes in different VRFs, route targets can be used to share routes among them. We can apply route targets to a VRF to control the import and export of routes.

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In case of configuring VRF lite, while RD is mandatory to be configured, RT configuration may not be required. Additionally, Route target may be categorized into 2 types –

Export Route target and Import Route target respectively.

Comparison Table: RD vs RT

Below table summarizes the differences between RD and RT

PARAMETERRDRT
Abbreviation for
Route Distinguisher
Route Target
Definition
64-bit identifier prepended to IPv4 route used to identify VPN the route belongs to
64-bit identifier used as part of MP-BGP attribute (extended community) to identify which route should be exported or imported to specific VPN.
Required in VRF Lite
Yes
Not required
Same value across different VPNs
No
May be same across multiple VPNs especially when using shared services.
Types
No further subtypes
2 Types –
* Export Route target
* Import Route target
Configuration example
ip vrf
rd 1:1
ip vrf
rd 1:1
route-target import 100:100
route-target export 100:100

Download the difference table here.

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