topic Questions about ACLs in ASA in Network Security

Questions about ACLs in ASA

nevereturn — Mon, 11 Mar 2019 22:43:58 GMT

I have 2 two questions:

The first question:
I have make an ACL entry inactive for test. For example I setup an ACL:

access-list out-in extended permit tcp host 2.2.2.2 host 1.1.1.1 eq telnet

access-list out-in extended permit tcp host 2.2.2.2 host 1.1.1.1 eq www

Then, I disable the ACL entry about the telnet one:

access-list out-in extended permit tcp host 2.2.2.2 host 1.1.1.1 eq telnet inactive

Now, how can I re-activate the entry about the telnet one without removing and re-write the ACL?

The second question:

Can I edit the specific ACL entry like router? In this case, how can I edit the entry about telnet. such as change the source IP and destination IP?

Thanks in advance!

Re: Questions about ACLs in ASA

malikyounas — Mon, 19 Mar 2012 10:09:57 GMT

1. you just need to enter the same command without 'inactive' at the end of it, do 'sh access-list' and get an idea of line number

access-list out-in line XX extended permit tcp host 2.2.2.2 host 1.1.1.1 eq telnet

2. Enter the command 'sh access-list', it will show all the active ACLs and the line number along with it, you will have to remove that line entry and re-add it, so say for example if you want to remove line from the following

ASA1# sh access-list

access-list cached ACL log flows: total 0, denied 0 (deny-flow-max 4096)

alert-interval 300

access-list inside_in; 2 elements; name hash: 0xd3a8690b

access-list inside_in line 1 extended permit ip any any (hitcnt=0) 0xb80bc887

access-list inside_in line 2 extended permit tcp host 2.2.2.2 host 1.1.1.1 eq telnet (hitcnt=0) 0x7bf0c01d

you can

config t

no access-list inside_in line 2 extended permit tcp host 2.2.2.2 host 1.1.1.1 eq telnet

access-list inside_in line 2 extended permit tcp host host eq telnet

Questions about ACLs in ASA

nevereturn — Mon, 19 Mar 2012 10:37:09 GMT

I've tested it.

The information you provided is very helpful.

Thanks very much!

Questions about ACLs in ASA

nevereturn — Mon, 19 Mar 2012 11:07:56 GMT

Hello Malikyounas,

Sorry for another question:

I found 2 parameters after access-list name: Extended and Standard.
I noticed that if I didn't define this parameter and just write the source IP, Dest IP, Protocl and so on, when I use "show access-list", it shows as an extended ACL.

So, if I don't define Extended or Standard, it will be an extended ACL by default? Or, it is related to different software version of ASA?

Thanks in advance.

Questions about ACLs in ASA

malikyounas — Mon, 19 Mar 2012 11:18:07 GMT

Hi,

Its better defined in this cisco doc where it says you cant use standard ACL as it only identifies the destination IP address which you can suppose is not enough for FW

Information About Standard Access Lists

Standard access lists identify the destination IP addresses of OSPF routes and can be used in a route map for OSPF redistribution. Standard access lists cannot be applied to interfaces to control traffic.

http://www.cisco.com/en/US/docs/security/asa/asa82/configuration/guide/acl_standard.html#wp1074591

Questions about ACLs in ASA

nevereturn — Mon, 19 Mar 2012 11:50:43 GMT

Hello malikyounas,

Thanks for the reply. Your information about standard ACLs is very helpful.

What I want to know is if I don't define Extended or Standard, it will be an extended ACL by default?

Thanks in advance.

Questions about ACLs in ASA

malikyounas — Mon, 19 Mar 2012 12:14:54 GMT

it will depend on what sort of entry you are going to add, if you add just the detiantion IP, ASA will consider as Standard and if you define source and destirnation, ASA will automatically consider this as extended.

access-list cisco permit ip host 20.20.20.1 - ASA will default to standard ACL for this

access-list cisco permit ip any host 20.20.20.1 - ASA will default to Extended ACL for this

if you use use show access-list after adding both ACLs above, you will see first one as standard and second as extended.

Questions about ACLs in ASA

nevereturn — Mon, 19 Mar 2012 12:49:44 GMT

Hello Malikyouns,

Thanks for your feedback.

It is very helpful.

Many thanks.