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GT&T Woes : Losing connectivity after couple seconds with public dhcp reservation from GT&T April 9, 2008

Posted by daakeung in Cisco.
Tags: , , ,

here we go again……..sigh……..why why why why, but why……lol.
A company I work for have been trying to setup a vpn connection using dsl for quite some time now (close to 2 years). Apparently, the way GT&T assigns a static public ip address to the dsl line, is by DHCP reservation. Now this has to be matched to your mac address, putting all this gibberish aside. When you get the lease, ip connectivity works for a few seconds and drops, keep in mind we are using a cisco 1811 router.

When preforming a debug dhcp:

The lease time shows as

*Mar 31 17:58:54.307: DHCP: SRequest placed lease len option: 0

This looked strange, so I called them up and they said that leases last for 30 mins.

so I manually configured the interface as follows:

interface FastEthernet0
ip dhcp client lease 0 0 30

ip address dhcp

duplex auto

speed auto

Release and renewed the lease

The debug dhcp outputted:
*Mar 31 18:02:33.859: DHCP: SRequest placed lease len option: 1800

So far connectivity has been up, and it hasn’t fallen off (as yet)

Hope this has been helpful.



1. DWM - April 30, 2008

Are ports 80, 443, 25 and 110 still blocked when you have a static address for GT&T’s DSL?

2. daakeung - April 30, 2008

last I checked, those ports are blocked inbound only.
I will double check and update you on this.

Their dedicated plan that is suppose to be for this is around 1200 us for 64k dedicated. Dunno how one is suppose to handle any amount of traffic on this cost and bandwidth.

I see your interest has to do with email and web, given that alot of internet e-mail is spam, that alone would kill your bandwidth. Even if you are filtering, some spam techniques used in spamassassin or the barracuda require an outbound connecting for dns black list….so mail can be considerable slow. Most of the cases when mail passes the dns black list filter, it might fail other tests and become marked as spam. So the mail definitely needs to be downloaded to be checked. Also outside clients receiving and sending mail, imagine what the mail experience would be like. Okay I am getting off topic here. Will double check those ports for you.

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