Adding DHCP option 156 and option 4 to Cisco Router

[Forum]

If you are using a Cisco Router as a DHCP server, you can still set it to offer option 156.

Within the 'DHCP Pool'
add this:
option 156 ascii "ftpservers=192.168.1.x, country=1, language=1, layer2tagging=0, vlanid=0"

If you want to add DHCP option 4 (SNTP time server)
add this:
option 4 ip 131.107.1.10 (or IP of your Time Server)

[Justin Phillips]

This just goes to show that I should check this forum more often. I ran into this issue the other day and it took me some time to get through. We had a problem for some reason with the option 4. The Cisco routher showed it was locked with a time source in Chicago and was showing Central Time (we are in Minnesota) and was in daylight savings mode, however the ShoreTel phones were 1 hour off. We eventually made an entry in the custom file for the 230 and 560 phones (sbbcustom and s6custom I think) and entered snmp 192.168.1.X or whatever your time server is and that worked too.

[Brian]

Option 156 on a Cisco 1841 router ver 12.4

I'm installing a similar configuration from posts on this forum about using DHCP on a Cisco router....


ip dhcp pool Shoretel
network 192.168.5.0 255.255.255.0
default-router 192.168.5.1
option 4 ip 192.168.0.15
dns-server 192.168.0.5
option 156 ascii "ftpservers=192.168.0.15, country=1, language=1, layer2tagging=0,vlanid=0"
option 2 hex ffff.8f80

ip dhcp excluded 192.168.5.1 192.168.7.50

With option 156 in the configuration, DHCP doesn't work and the phones do not recieve an IP until I remove it from the configuration.

Does anyone know if the option is limited to certain routers?

[mattwray]

I'm installing a similar configuration from posts on this forum about using DHCP on a Cisco router....


ip dhcp pool Shoretel
network 192.168.5.0 255.255.255.0
default-router 192.168.5.1
option 4 ip 192.168.0.15
dns-server 192.168.0.5
option 156 ascii "ftpservers=192.168.0.15, country=1, language=1, layer2tagging=0,vlanid=0"
option 2 hex ffff.8f80

ip dhcp excluded 192.168.5.1 192.168.7.50

With option 156 in the configuration, DHCP doesn't work and the phones do not recieve an IP until I remove it from the configuration.

Does anyone know if the option is limited to certain routers?

You are putting the phones into VLAN 0 which is probably not configured... What VLAN are your phones supposed to be in? You have also turned off layer 2 tagging which you should keep on if you are using VLANs.

[mattwray]

If you are using a Cisco Router as a DHCP server, you can still set it to offer option 156.

Within the 'DHCP Pool'
add this:
option 156 ascii "ftpservers=192.168.1.x, country=1, language=1, layer2tagging=0, vlanid=0"

If you want to add DHCP option 4 (SNTP time server)
add this:
option 4 ip 131.107.1.10 (or IP of your Time Server)

If you are not using VLANs I believe you should set the vlanid to 1 which is the default vlan in cisco....

[aspen]

Your could try adding the older 66 option for the ip 100 and dropping the 156 if you don't need vlan tagging.

option 66 ascii "192.168.1.10" would be the format. I know it still worked for the 530/560/110 under 6.0. I never tried it with a 230. But that does not mean they will support it forever.

As for the option 156 I don't think 0 is the null value. It may be "null" or just nothing at all. You might try play around with different values for null.

[tnshurtm]

Could it be the dhcp excluded statement? Is that a range or list? why the 7?

[Forum]

Could it be the dhcp excluded statement? Is that a range or list? why the 7?

That's a good eye...

ip dhcp excluded 192.168.5.1 192.168.7.50

this would exclude the entire 192.168.5.1 - 192.168.7.50 RANGE from being issued.

Issue the ip dhcp excluded-address command to exclude IP
!--- addresses from being assigned by the DHCP server.

Wonder if it's just a typo.

Charles

[Brian]

Found a solution

I'm installing a similar configuration from posts on this forum about using DHCP on a Cisco router....


ip dhcp pool Shoretel
network 192.168.5.0 255.255.255.0
default-router 192.168.5.1
option 4 ip 192.168.0.15
dns-server 192.168.0.5
option 156 ascii "ftpservers=192.168.0.15, country=1, language=1, layer2tagging=0,vlanid=0"
option 2 hex ffff.8f80

ip dhcp excluded 192.168.5.1 192.168.7.50

With option 156 in the configuration, DHCP doesn't work and the phones do not recieve an IP until I remove it from the configuration.

Does anyone know if the option is limited to certain routers?

I found that the small Cisco 1700 router I was trying to configure for DHCP could not handle all of those lines. I removed "option 2 hex ffff.8f80" and it worked like a charm... I'm thinking it had to do with placing too much on the router to issue out all of those lines...

Thanks for all of the great suggests. I hope this helps some one else.

[Jlowe]

Option 4 or Option 42

Is there a difference in option 4 and option 42. I have always used 42, as i was looking for an actual NTP. Advice?