10-02-2006 02:24 PM
Dear All,
I HAVE cisco 1841.
it has 2 interfaces.
the first one which is f 0/0 is have public ip from my ISP.
the other one is normal, and i am going to give it 192.168.1.100 / 24.
now i have 3 subnets totally diffrent .
i want to create 3 subinterfaces from f0/1.
my question is , how many subinterfaces can i add under the f 0/1 ?
and can i make this Router work as NAT ( overloading ) but all the 4 subnet will use the same public IP Address ?
can it be done as per this diagram ?
please update me.
10-02-2006 04:25 PM
You can issue the "show idb" command (Interface Descriptor Block) to determine how many subinterfaces your router will theoretically support. Each subinterface uses one IDB. Your router should support a few hundred although it may not be recommended to run that many.
As far as overloading for NAT (aka PAT) from multiple inside interfaces you shouldn?t have a problem. Just be aware there is a limit to the number of connections the single outside interface can concurrently support.
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
10-14-2006 03:37 PM
>> show idb <<
Maximum number of IDBs 300
24 SW IDBs allocated (2584 bytes each)
19 HW IDBs allocated (4696 bytes each)
HWIDB#1 1 Ethernet0/0 (HW IFINDEX, Ether)
HWIDB#2 2 Serial0/0 (HW IFINDEX, Frame relay, Serial)
HWIDB#3 3 BRI0/0 (HW IFINDEX, HW ISDN, Serial)
HWIDB#4 4 BRI0/0:1 (HW ISDN, Serial)
HWIDB#5 5 BRI0/0:2 (HW ISDN, Serial)
HWIDB#6 6 Serial1/0 (HW IFINDEX, BSTUN, Serial)
HWIDB#7 7 Serial1/1 (HW IFINDEX, BSTUN, Serial)
HWIDB#8 8 Serial1/2 (HW IFINDEX, Serial)
HWIDB#9 9 Serial1/3 (HW IFINDEX, Serial)
HWIDB#10 10 Dialer1 (HW IFINDEX, HW COMPRESS, Serial)
HWIDB#11 11 Dialer2 (HW IFINDEX, HW COMPRESS, Serial)
HWIDB#12 12 Loopback111 (HW IFINDEX)
HWIDB#13 13 Loopback1111 (HW IFINDEX)
HWIDB#14 14 Loopback1112 (HW IFINDEX)
HWIDB#15 15 Loopback2222 (HW IFINDEX)
====================
yes you can nat all 4 subnets but i ssuppose performance would be affected .
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