Routing (2) /27 IP block with 2 different customer from a /24 IP block.

[betanscribe97]

Hi guys,

I am a routing technician working for a ISP, Customer has there own /24 IP block [yy.xx.xx.xx/24] directly from ARIN. And wishes to subnet that into (2) /27 IP block for two different site location.   That would be facing two differnt interface from a two different PE router. I am granting them a dedicated WAN IP fro each of heir sites. For their Site A LAN they wish to use [yy.xx.xx.0/27] and for their Site B LAN they will use [yy.xx.xx.32/27] . Can i set statically each of the /27 on my each of the specific PE router facing each of the 2 customer sites, or i will just have to set the whole [yy.xx.xx.xx/24] to both of the 2 PE router facing the 2 customer site. Thank you for your support.

[Giuseppe Larosa]

Hello Jonathan,

>> Can i set statically each of the /27 on my each of the specific PE router facing each of the 2 customer sites

You need to make each PE node able to route to the specific co-located /27 IP subnet, you can use a static route for this or you can receive the specific route on a eBGP session from CE.

In any case at BGP level the aggregate route /24 has to be generated or received at the two PE nodes.

The /24 block is needed for correct propagation of the customer route in the public Internet

Hope to help

Giuseppe

[betanscribe97]

Hi Sir,

Thanks for your reply.

Another question is, if customer is unwilling to do eBGP on their end.

Can they just use yy.xx.xx.xx/27 statically routing from each of their sites, while on my PE node, i'll do the same statically.

WAN IP 1: n.n.n.0/30

WAN IP 2: n.n.n.4/30

e.g.

customer router site 1:

ip route yy.xx.xx.xx 255.255.255.224 n.n.n.1(next hop, GW of PE 1)

PE side 1:

ip route yy.xx.xx.xx 255.255.255.224 n.n.n.2(next hope,  CE side 1)

customer router site 2

ip route yy.xx.xx.xx 255.255.255.224 n.n.n.5(next hope, GW of PE 2)

PE side 2:

ip route yy.xx.xx.xx 255.255.255.224 n.n.n.6(next hope, CE side 2)