why need rd?

[chenleish]

rd is used to make the address distinguish,but i think use the rt , it can achieve the same purpose,

so why do we need both of rd/rt?

[Harold Ritter]

The RD and RT are two different things and need not be the same. There can be only one RD assigned to a VRF. On the other hand, there can be many RTs assigned to a VRF. Tying the RD to the RT would lead to less flexibility.

Hope this helps,

[jayjorda]

Using the RT does not make the addresses unique when placed in the global routing table of the PE. The RD does this. So you can't use the RT in place of the RD. The RD is what converts the address from an IPv4 address to a VPNv4 address by appending the RD to the front of the address. So this now makes the addresses unique when placed in the global table. RTs on the other hand are just extended community tag values that you utilize to import and export prefixes tou your vrf.

Jay

[ellemen]

there are 2 things have to be made clear:

1)VRF routes will never be placed in global routing table of PE unless u do leaking

2)RD only stand for VRF, on different VRF, IP address need not to be unique unless u do routing between them