HSRP and DHCP

Published on January 4 2014 by dellpe

Question:

I am new to Cisco and I am having few problems in configuring my topology in Packet tracer.

I am having redundancy in router and swithes both,

I have assigned one layer2 2960 switch as a VTP server and asssigned VLANs from that switch then assigned ports to the hosts in access layer switches.

Problem 1: If I take my Router1 off I am unable to ping so the pupose of having redundant router does not serve the pupose.

Problem 2 : I need to assign DHCP server for the users who will be connecting wirelessly with Access Points, so can I configure DHCP on Access Points which I am unable to do so in Packet tracer any idea how? / Or shall I configure the DHCP on Router1 and Router2 and exclude the addresses I have assigned to all the hosts connected using ethernet.

Also how can I configure Email server in this tolpolgy and where?

Answer:

you can't simply assign the same ip address to two different routed interfaces. You need to look at vrrp.

(1) You need to configure either HSRP (Hot standby routing protocol) or VRRP (Wirtual routing redundancy protocol), or GLBP (Gateway load balancing protocol).

With either of this config, you will be able to configure 1 logical IP address, which will act as a gateway on your computers. However, both routers will need different IP's (all within the same subnet). You will also need to create multiple HSRP groups to support all your VLAN's. So one HSRP group per VLAN. The logical IP in the HSRP group will act as the default gateway on computers within the VLAN.

Though I don't think packet tracer supports any of the above configs - FYI it's part of the CCNP Switch sylabus. So the above explaination will make sense after you've got a good understanding of HSRP, VRRP and/or GLBP.

(2) I would recommend setting both the Router as a DHCP server, and configure the Access Point (AP) with a static IP (disable NAT and DHCP on the AP)

(3) In packet tracer, choose the Server icon and check it's properties. You should find an option to enable EMAIL server. Connect it to any of the Distribution layer switches.

Sample Configure

DHCP POOL CONFIGURED ON BOTH R1 and R2

ip dhcp excluded-address 192.168.1.1 192.168.1.5 ( Exclude the IP's that we do not want allocated out )

ip dhcp pool 3anetwork.com
network 192.168.1.0 255.255.255.0 (Define the network scope we want to give out )
default-router 192.168.1.1 ( The default router is the virtual IP that we setup for HSRP )