10-02-2006 02:20 PM - edited 03-05-2019 12:04 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 09:48 PM
issue the "show idb" command to see how many subinterfaces your router supports. Your diagram certainly looks doable. I don't know if your router can actually handle NATing for 1000 IPs.
A couple points on your diagram. It looks like you have four subnets. You need to move your first network off of the physical interface to a sub-interface. You really shouldn't be using public IP space on your inside network. Does your diagram show your old and new network?
10-02-2006 11:56 PM
THanks for your reply.
i have the followig results.
=============================================
HO-RO-Internet#sh idb
Maximum number of Software IDBs 1200. In use 12.
HWIDBs SWIDBs
Active 6 6
Inactive 6 6
Total IDBs 12 12
Size each (bytes) 2904 1280
Total bytes 34848 15360
Type SIdx Idx St,O,Sh Interface Name (subblocks)
---------------------------------------------
H 1 1 U,D,R FastEthernet0/0 (HW SB CDP(4), MAC ADDR(2), Ether(1))
H 2 2 U,D,R FastEthernet0/1 (HW SB CDP(4), MAC ADDR(2), Ether(1))
H 3 3 A,D,R Serial0/0/0 (HW SB CDP(4), Serial(3))
H 4 6 U,D,R Loopback0
H 5 7 U,D,R Loopback1
H 6 8 U,D,R Loopback3
S 1 3 U FastEthernet0/0 (SW CDP(5), DSS(4), Dynamic DNS Updates(3
), NetBIOS(2), KEEPALIVE(1))
S 2 4 U FastEthernet0/1 (SW CDP(5), DSS(4), Dynamic DNS Updates(3
), NetBIOS(2), KEEPALIVE(1))
S 3 5 U Serial0/0/0 (SW CDP(5), NetBIOS(2), KEEPALIVE(1))
S 4 9 U Loopback0 (KEEPALIVE(1))
S 5 10 U Loopback1 (KEEPALIVE(1))
S 6 11 U Loopback3 (KEEPALIVE(1))
Key: SIdx=Sort Index, Idx=hw_if_index or if_number
St=Current State, O=Old State, Sh=Shadow State
A=Admindown, D=Down, G=Going Down, I=Init
R=Reset, T=Testing, U=Up, X=Deleted
HO-RO-Internet#
===========================================
so, from where can i know how many sub-interfaces i have ?
please update me .
10-03-2006 05:28 AM
Your question changed from "can add" to "I have."
From your output, you can have 1200 total interfaces. You will likely run into memory issues before you hit 1200 interfaces.
10-03-2006 03:47 AM
YES,
it can be done. a few notes though.
your F0/0 interface will not have an ip address on it. (only the f0/0.1, f0/0.2..etc)
if you use subinterfaces, you only put ip addresses on those.
(likewise, if you do not use subinterfaces, you would put an ip address on F0/0)
you can then enable NAT to provide internet acceess for all of your subnets. you will create a nat pool that all subnets are assigned too and then use an 'ip nat inside source list....overload' command. see the link below for an more NAT info:
also, you can configure a subinterface for each VLAN you need to configure.
(since your interface will be supporting multiple vlans, it will be using 802.1q and the switch port it connects to will have to be configured as a 802.1q trunk as well)
you can easily tell how many subinterfaces you have by either 'show run' and count them up, or 'show interfaces' and count them.
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