Hi everybody
I am reading about how to configure cisco router as dhcp server and troublshoot any issue related to it
I performed this lab as shown below:
R1--f0/0-199.199.19.0--R2---198.198.198.0----R4
R1 is configured as dhcp client
R2 is dhcp relay agent
R4 is dhcp server.
R1 f0/0 mac address: c000.211c.0000
Below is dhcp ack sent by R4( dhcp server) to R2( relay agent):
No. Time Source Destination Protocol Length Info
760 2618.315000 198.198.198.4 199.199.199.2 DHCP 342 DHCP ACK - Transaction ID 0x1208
Frame 760: 342 bytes on wire (2736 bits), 342 bytes captured (2736 bits)
Ethernet II, Src: c0:03:21:1c:00:00 (c0:03:21:1c:00:00), Dst: c0:01:21:1c:00:10 (c0:01:21:1c:00:10)
Internet Protocol Version 4, Src: 198.198.198.4 (198.198.198.4), Dst: 199.199.199.2 (199.199.199.2)
User Datagram Protocol, Src Port: bootps (67), Dst Port: bootps (67)
Bootstrap Protocol
Message type: Boot Reply (2)
Hardware type: Ethernet
Hardware address length: 6
Hops: 0
Transaction ID: 0x00001208
Seconds elapsed: 0
Bootp flags: 0x8000 (Broadcast)
Client IP address: 0.0.0.0 (0.0.0.0)
Your (client) IP address: 199.199.199.1 (199.199.199.1)
Next server IP address: 0.0.0.0 (0.0.0.0)
Relay agent IP address: 199.199.199.2 (199.199.199.2)
Client MAC address: c0:00:21:1c:00:00 (c0:00:21:1c:00:00)
Client hardware address padding: 00000000000000000000
Server host name not given
Boot file name not given
Magic cookie: DHCP
Option: (t=53,l=1) DHCP Message Type = DHCP ACK
Option: (t=54,l=4) DHCP Server Identifier = 198.198.198.4
Option: (t=51,l=4) IP Address Lease Time = 1 day
Option: (t=58,l=4) Renewal Time Value = 12 hours
Option: (t=59,l=4) Rebinding Time Value = 21 hours
Option: (t=12,l=13) Host Name = "R1.lab.local."
Option: (t=1,l=4) Subnet Mask = 255.255.255.0
End Option
Padding
Above we can see R1 f0/0 is being assigned 199.199.199.1. Lets confirm it.
R1#show ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 199.199.199.1 YES DHCP up up
Now When I check the dhcp binding at R4, I should have found 199.199.199.1----> c0:00:21:1c:00:00 ( R1 f0/0 mac address)
However, I found something completely different:
R4#show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
199.199.199.1 0063.6973.636f.2d63. Mar 02 2002 12:57 AM Automatic
3030.302e.3231.3163.
2e30.3030.302d.4661.
302f.30
None of the highlighted mac address matches the R1 f0/0 mac c0:00:21:1c:00:00
What is the issue here?
why do we have more than one mac bind to 199.199.199.1?
Where do these mac addresses come from?
thanks and have a great day.
Solved! Go to Solution.
Hello Sarah,
please try this command
R4#show ip dhcp binding 199.199.199.1 and see what is the output.
thanks
hello Sarah,
its look like its default server automatic behaviour.
if you do
# debug ip dhcp server packets
it will show you in loggs that 0063.6973.636f.2d63.3030.302e.3266.6130.2e30.3030.302d.4661.302f.30 is one mca adress
R2#
*Oct 24 16:44:19.015: DHCPD: Sending notification of DISCOVER:
*Oct 24 16:44:19.015: DHCPD: htype 1 chaddr 0018.b9cd.bef0
*Oct 24 16:44:19.015: DHCPD: remote id 020a0000ac10170200000000
*Oct 24 16:44:19.015: DHCPD: circuit id 00000000
4 - 15 CCNP: Building Scalable Internetworks v5.0 - Lab 5-5 Copyright 2006, Cisco Systems, Inc
*Oct 24 16:44:19.015: DHCPD: DHCPDISCOVER received from client
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30 on
interface FastEthernet0/0.
*Oct 24 16:44:19.015: DHCPD: Seeing if there is an internally specified pool
class:
*Oct 24 16:44:19.015: DHCPD: htype 1 chaddr 0018.b9cd.bef0
so in end you will get similar answer.
R2# show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
172.16.23.101 0063.6973.636f.2d30. Oct 25 2006 10:20 PM Automatic
3031.382e.6239.6364.
2e62.6566.302d.4661.
302f.30
you can try manual binding if you want hope fully this will bit diffrent.
thanks
Hi Sarah,
this string is not the MAC address but the client-identifier.
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30
is cisco-0018.b9cd.bad0.Fa0/0 in Hex.
You can change this behaviour with the command ip address dhcp client-id fastethernet0/0 and then you'll see the MAC
address of the interface as client-identifier.
Regards.
Alain
Don't forget to rate helpful posts.
Hi,
63 in hex is 99 in decimal and the ascii code for decimal 99 is lower case c
69 in hex is 105 in decimal which is ascci code for lowercase i. and so on...
Regards.
Alain
Don't forget to rate helpful posts.
Hi Sarah,
http://blog.ioshints.info/2007/08/default-dhcp-client-id.html
Regards.
Alain
Don't forget to rate helpful posts.
Hello Sarah,
please try this command
R4#show ip dhcp binding 199.199.199.1 and see what is the output.
thanks
Hi Singh
I recreated the lab as shown below, still same result.
R1 f0/0----------f0/0--R2---------------------R3
R1 dhcp client
R2 dhcp relay agent
R3 dhcp server.
R3#show ip dhcp binding 199.199.199.1
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
199.199.199.1 0063.6973.636f.2d63. Mar 02 2002 12:06 AM Automatic
3030.302e.3266.6130.
2e30.3030.302d.4661.
302f.30
R1#show int f0/0
FastEthernet0/0 is up, line protocol is up
Hardware is Gt96k FE, address is c000.2fa0.0000 (bia c000.2fa0.0000)
R1#show ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 199.199.199.1 YES DHCP up up
Thanks
hello Sarah,
its look like its default server automatic behaviour.
if you do
# debug ip dhcp server packets
it will show you in loggs that 0063.6973.636f.2d63.3030.302e.3266.6130.2e30.3030.302d.4661.302f.30 is one mca adress
R2#
*Oct 24 16:44:19.015: DHCPD: Sending notification of DISCOVER:
*Oct 24 16:44:19.015: DHCPD: htype 1 chaddr 0018.b9cd.bef0
*Oct 24 16:44:19.015: DHCPD: remote id 020a0000ac10170200000000
*Oct 24 16:44:19.015: DHCPD: circuit id 00000000
4 - 15 CCNP: Building Scalable Internetworks v5.0 - Lab 5-5 Copyright 2006, Cisco Systems, Inc
*Oct 24 16:44:19.015: DHCPD: DHCPDISCOVER received from client
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30 on
interface FastEthernet0/0.
*Oct 24 16:44:19.015: DHCPD: Seeing if there is an internally specified pool
class:
*Oct 24 16:44:19.015: DHCPD: htype 1 chaddr 0018.b9cd.bef0
so in end you will get similar answer.
R2# show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
172.16.23.101 0063.6973.636f.2d30. Oct 25 2006 10:20 PM Automatic
3031.382e.6239.6364.
2e62.6566.302d.4661.
302f.30
you can try manual binding if you want hope fully this will bit diffrent.
thanks
Hi Sarah,
this string is not the MAC address but the client-identifier.
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30
is cisco-0018.b9cd.bad0.Fa0/0 in Hex.
You can change this behaviour with the command ip address dhcp client-id fastethernet0/0 and then you'll see the MAC
address of the interface as client-identifier.
Regards.
Alain
Don't forget to rate helpful posts.
Thanks Alain
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30
is cisco-0018.b9cd.bad0.Fa0/0 in Hex.
The highligted numbers are already in hex
How can we say
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30
is cisco-0018.b9cd.bad0.Fa0/0 in Hex.?
Hi,
63 in hex is 99 in decimal and the ascii code for decimal 99 is lower case c
69 in hex is 105 in decimal which is ascci code for lowercase i. and so on...
Regards.
Alain
Don't forget to rate helpful posts.
Hi Alain
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30
You are saying the above string is in hex, and its ASCI representation is:
cisco-0018.b9cd.bad0.Fa0/0
Is that correct?
But i thought mac address is written in hex.
thanks
Hi Sarah,
http://blog.ioshints.info/2007/08/default-dhcp-client-id.html
Regards.
Alain
Don't forget to rate helpful posts.
thanks Alain. I got it. Nice link