internet connection using GRE

Unanswered Question
Feb 5th, 2007

Hi everyone,

is there any harm in using GRE tunnel for internet connectivity between my router and ISP router ?

earliest reponse will be highly appreciated.



I have this problem too.
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gaurav.prakash@... Mon, 02/05/2007 - 05:57

No harm usually, just use the following command with discussion from ur ISP to avoid any prob..

1. ip tcp adjust-mss

2. Also you might need to lower the interface mtu setting to ..



aryan1980 Mon, 02/05/2007 - 06:28

Thanks a lot for both of u guarav n leo,

let me try n i'll revert back if there is any query



Danilo Dy Mon, 02/05/2007 - 07:08

Depends on your connection.

If your connection to your ISP is direct link or P2P, I dont see the need to use it.

However if there is a multiple-hop between you and your ISP (i.e. MPLS) you can consider using it.

My experience with GRE (in order of implementation);

1. I use it heavily in MPLS

- From main to ISP using eBGP.

- From production to disaster recovery sites using iBGP and OSPF.

- From main office to multiple sites using static and OSPF. So I don't have to pay service charge to MPLS provider whenever I need to add a new network/subnet to route. I control the routing.

- Actual failover tested.

2. I use it from main office to overseas remote sites with the following;

- Internet as primary (because its cheap) with IP GRE over IPSEC

- ISDN as backup with IP GRE over IPSEC

- Actual failover tested

Anything that has multi hop that bothers you, use Cisco router and implement IP GRE

You can be creative how to use IP GRE to your network benefits (and cost saving). I don't see any problem with IP GRE, the DF problem can be fixed by a single command line.


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