In our office in the little old place known as England, we use Cisco 7941 and will soon to begin using 7942 Cisco SCCP IP Phones . The company uses Cisco Call Manager 6 or CUCM for those in the know. In our local office we are using a Cisco technology called SRST or Survivable Remote Site Telephony.
This technology, SRST allows our IP handsets to fallback to operating with a locally situated CME or Call Manager Express device so that if our Internet connection to our corporate head office fails then we still have limited telephony functionality.
One issue that has always plagued us here is that our phones would show the US time and date from our West Coast, San Jose based CUCM. Although only a minor issue it meant that call logs didn’t show the time you would expect nor did the phone if you wanted to look at the time.
When speaking to our IT department they couldn’t put their finger on a fix, so after researching online initially I suggested to them that a Device Profile be created on the CUCM to force the handsets to use United Kingdom locale instead of the US one. The change was implemented but the phones still show the US time, so what gives?
Upon reading some more information online today, I discovered that the key is the SRST device: A Cisco 2801 Integrated Services Router in our case. When a phone is associated with an SRST device, the SRST registers itself as an additional CUCM on the phone. For me, this appears as a third Call Manger as we have an Active and a Standby Call Manager in a cluster in our US office. When using SRST, the phone knows that the SRST device will always be closer geographically to the phone than the CUCM, hence the whole point of having SRST and once this is established, the phone will always learn the date and time from it’s local device.
Using the following command on the router I was able to see the problem that when the router was configured by our US colleagues they left the time zone setting on the router to Pacific by default, which would seem normal for them:
uk-srst#show clock 05:01:44.254 PST Fri Aug 13 2010 uk-srst#
This means that the time zone on the SRST 2801 needs to be changed to GMT for our country, England, correctly. This is done using two commands – The first command sets the time zone to GMT. The second command enables summer time or daylight savings as some call it, and uses the BST or British Summer Time variant of daylight savings:
uk-srst#config t uk-srst(config)#clock timezone GMT 0 uk-srst(config)#clock summer-time BST recurring uk-srst(config)#end uk-srst# uk-srst#show clock 13:01:44.254 BST Fri Aug 13 2010 uk-srst#
As you can see from the IOS output above, after entering the two commands, the clock is now using BST for British Summer Time. Saving the running configuration and then rebooting all of the effected SCCP IP Phones will apply the new date and time zone settings accordingly.