thanks for your reply.kindly tell me the model no.should be cisco(less than 100 and also 100 user)

u can use ASA or IOS firewall

both good

but there is a cisco routers seriese called ISR which is exacly all in one also in diffrent sizes this works for voice, security like IPS, firewall and much more cpabilities in one box

ISR 1800:

http://www.cisco.com/en/US/products/ps5853/index.html

ISR 2800:

http://www.cisco.com/en/US/products/ps5854/index.html

ASA:

http://www.cisco.com/en/US/prod/collateral/vpndevc/ps6032/ps6094/ps6120/prod_brochure0900aecd8048dba8.html

IOS:

http://www.cisco.com/en/US/products/sw/secursw/ps1018/index.html

good luck

if helpful Rate

ASA/PIX will be good..

Except ASA 5505 , all other supports unlimited users in Base License in 8.0 software

PIX 515,525,535 all supports unlimited users in Restricted , Unrestricted , Failover, Active-Active failver licenses.. in 8.0 software

But in 7.0 it has limitations like

ASA 5510 32K concurrent connections

ASA 5520 130K -----"-------

ASA 5540 280K -----"-------

PIX 515 48K -----"-------

PIX 525 140K -----"-------

PIX 535 250K -----"-------

See below link for more information of licensing..

http://www.cisco.com/en/US/docs/security/asa/asa80/configuration/guide/specs.html

http://www.cisco.com/en/US/docs/security/asa/asa70/configuration/guide/specs.html

HTH...rate if helpful..