Subnetting, private networks & default routes

chriswaltham · 2006-04-22T16:49:17+00:00

I'm (still) having a little trouble wrapping my head around the conceptof subnet masks; specifically in a large private network.I administer a bunch of machines and networks, most of them beginningwith 172.16 but a couple starting with 172.30. They are all connectedvia circuits: T1s, Frame Relays and VPNs. The core network is172.16.1.0, and one example remote network is 172.16.130.0. The troubleis that, despite the two nets being connected via Frame Relay, the corenet can ping the remote net but the remote net can't ping hosts in thecore net.All devices in the core net (172.16) have netmasks of 255.255.0.0, butthe machines in the remote net have netmasks of 255.255.255.0. Is thispart of the problem that I'm facing? I inherited this job onlyrecently, and as such I didn't make the initial routing & subnettingdecisions. Because I have machines in 172.16 and 172.30 networks, and Iwant all machines to be able to communicate with each other, should Ijust convert all netmasks into 255.0.0.0 to eliminate the problems I'mfacing?TIA and HAND,Chris

Apr 22, 2006 22 Replies

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Chris 20 years ago

I am thinking about using helper-address in the future, as I am contemplating (but haven't decided for sure, yet) about passing DHCP leases from the main site (aka the 2516) out to the remote site. IIRC, though, you can explicitly configure helper-address to pass only certain types of broadcast traffic... right?

Chris

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Barry Margolin 20 years ago

Right, with "ip forward-protocol". Anyway, once the broadcast is relayed using helper-address, it's no longer a broadcast (unless the helper-address is a directed broadcast address of one of the router's other interfaces).

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