In scenarios where Internet access is provided by cable providers or local vendors, generally the [p2p type=”slug” value=”ip-addressing-scheme-ipv4"]IP address[/[/p2p]ssigned to Cisco CPE at home is via [p[p2p type=”slug” value=”dhcp-dynamic-host-configuration-protocol”]trong>DHCP[/[/p2p]By default Cisco Router is assigned IP address by DHCP on its Client ID.The Client ID has the format of “Cisco-[p[p2p type=”slug” value=”what-is-a-mac-address”]C address [/[/p2p]strong>”. However, this becomes a cumbersome job at times for Internet provider and customer to manage Client ID or perform troubleshooting on the same. Cisco has devised a solution to this problem. It has provision to replace Client ID with [p[p2p type=”slug” value=”what-is-a-mac-address”]trong>MAC address [/[/p2p] [p[p2p type=”slug” value=”dhcp-dynamic-host-configuration-protocol”]trong>DHCP[/[/p2p]lient. Now let’s see how this can be done –

1st, we see the mac address of [p[p2p type=”slug” value=”dhcp-dynamic-host-configuration-protocol”]trong>DHCP[/[/p2p]trong> Client(Cisco Router at Customer end) –

R1#show interface fa0/0 | incl biaHardware is Gt96k FE, address is c200.10fc.0000 (bia c200.10fc.0000) 

Now , we enable DHCP debugging on Cisco Router to view how [p[p2p type=”slug” value=”dhcp-dynamic-host-configuration-protocol”]trong>DHCP[/[/p2p]ommunication between Client and server happens –

R1#debug dhcp detail

Next , configure Client Router Interface Fa0/0 to get [p[p2p type=”slug” value=”ip-addressing-scheme-ipv4"]trong>IP address[/p2[/p2p]ough DHCP –

R1(config)#int fa0/0R1(config-if)#ip address dhcp

Debug displays below output –

*Mar  1 00:23:04.515:    DHCP Lease server:, state: 2 Requesting*Mar  1 00:23:04.519:    DHCP transaction id: 19D7

*Mar  1 00:23:04.519:    Lease: 86400 secs,  Renewal: 0 secs,  Rebind: 0 secs

*Mar  1 00:23:04.519:    Next timer fires after: 00:00:03

*Mar  1 00:23:04.519:    Retry count: 1   Client-ID: cisco-c200.10fc.0000-Fa0/0

*Mar  1 00:23:04.519:    Client-ID hex dump: 636973636F2D633230302E313066632E

*Mar  1 00:23:04.523:    303030302D4661302F30

As shown above , Client ID of Cisco Router is cisco-c200.10fc.0000-Fa0/0.

Now configure Router to use mac address as the Clinet ID –

R1(config-if)#ip address dhcp client-id FastEthernet 0/0
*Mar  1 00:24:58.699:    DHCP Lease server:, state: 2 Requesting*Mar  1 00:24:58.699:    DHCP transaction id: 1EFF

*Mar  1 00:24:58.703:    Lease: 86400 secs,  Renewal: 0 secs,  Rebind: 0 secs

*Mar  1 00:24:58.703:    Next timer fires after: 00:00:03

*Mar  1 00:24:58.703:    Retry count: 1   Client-ID: c200.10fc.0000

*Mar  1 00:24:58.703:    Client-ID hex dump: C20010FC0000

*Mar  1 00:24:58.707:    Hostname: R1

*Mar  1 00:24:58.707: DHCP: SRequest- Server ID option:

*Mar  1 00:24:58.707: DHCP: SRequest- Requested IP addr option:


Now we can see Cisco Router has been assigned [p2p[p2p type=”slug” value=”ip-addressing-scheme-ipv4"]ong>IP address[/p2p][/p2p] [p2p t[p2p type=”slug” value=”what-is-a-mac-address”]g>MAC address [/p2p][/p2p]strong>Client ID.

Please follow and like us:


Related Posts

Add Comment

Social Media Auto Publish Powered By :
Select your currency
USD United States (US) dollar

Checkout : E-STORE for latest release "JNCIP-SEC & JNCIA-SEC Interview Q&A " Dismiss