Question about isp change

Unanswered Question
Sep 23rd, 2009

We are changing our isp to another.

So I need to plug in the new Ip set for the outside interface and static route.

If I replace those along with the new mask is there anything else I should look for. I know I will have to change the wan ips for the nated hosts but will my acls follow automatically?


I have this problem too.
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Giuseppe Larosa Wed, 09/23/2009 - 12:36

Hello Said,

you need to update all parts of your configuration where public ip addresses appear.

There is no automatic update of ACLs you need to change them if needed = if public ip addresses appear in them.

if you are thinking of NAT acls depending on their formulation they may be left unchanged or they need a change.

Hope to help


assalihin Tue, 09/29/2009 - 07:25


Thanks for the input.

I have another question plese:

The connection I am dealing with a a t1 encapsulated ppp.

The isp pgave us a set

1- an isp and a customer ip addresses for the serial.

2- A set of public ips.

I did the serial part and the isp confirmed that the conection is up but iam having hard time configuring my eth interface so I can have access to the internet and email.

I know how to configure an interface but i am not getting to the internet!

Giuseppe Larosa Tue, 09/29/2009 - 11:44

Hello Said,

you should give a public ip address to the ethernet this should allow you to access the internet from hosts connected to it.

If you need more ip addresses then what you have you need to use NAT.

example nat overload

int se0/0

! your wan

int et0/0

! your DMZ public ip address here

int et0/1

! internal lan

NAT config:

int e0/1

ip nat inside

int se0/0

ip nat outside

ip nat inside source list 11 int se0/0 overload

access-list 11 permit private-ipaddress wildcard-mask

! that is the ip subnet on internal lan

! et0/1

Hope to help



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