Routing issue over internet

[Pawan Raut]

I have one /24 Public IP block which I am routing over over Primary Data center to Internet service provider.

Now I am building new Datacenter and I have used /26 Public IP subnet from that /24 IP block and I have asked my service provider to route /26 from  new DC but ISP has issue to route /26 from new DC they asked me they can route /24 from new DC.

Is this  really issue for ISP

e.g. situation as like below

1.1.1.0/24 DC1 --> ISP --> Internet 

1.1.1.192/26 DC2 --> ISP -- > internet

[Philip D'Ath]

You can not get global rout-ability unless you use a /24 or larger.  It is common practice amongst ISPs to drop anything smaller than a /24 to contain the routing table size.

However, as long as it is the same ISP you are connecting to in both cases, they should be able to have both a /24 route to the first DC, and a more specific /26 to the second DC.  This is assuming they don't drop routes smaller than a /24 themselves, have some kind of aggregation policy, etc.

Have you considered getting a link between the two DC's (even if it is a GRE tunnel), advertising the same /24 out of both, and then re-routing the traffic inside of your own network once you have received it?

[wingetjennifer881]

This requires 2 simple steps.
     i) A firewall policy to allow the packes to grom from WAN1->(whatever interface the public IP is behind)
     ii) a route to that public IPSince the default gateway is going to be out WAN1, then you need to route that IP another way.