Posts tagged Security
Hello everyone. I know I’ve been neglecting this blog for too long. Can’t promise that things are going to change, but I have a good post for today.
I was recently exposed to some new technology while working with a customer. I had to learn it pretty quickly. This post is about a new feature in the Cisco ASA 8.4 code called Bridge Groups. This is essentially the addition of BVI interfaces, which have existed in IOS forever. This feature is useful when running an ASA transparently, but not physically inline. Running a firewall physically inline works well, but it can limit you to the number of available interfaces you have on each firewall. Adding physical interfaces to a firewall is expensive. This feature also saves you from using a context per firewalled VLAN on your ASA. Here we’ll use a 3750 for physical connectivity and use BVIs to force traffic through the firewall. Here is the physical topology:
Dropping in to do a quick post today. Sorry for the ridiculous lack of content lately. I’ve been busy with finding/changing jobs and new responsibilites and all that.
Today I’m going to cover “object groups” on ASAs. I was never a big fan of these, which I realized had a lot to do with using them behind others, not actually writing them myself. It takes awhile (for me, at least) to wrap your head around what the person before you was trying to accomplish. This is what put me off object groups. Though, I discovered that if I write them myself, I love them, lol. They can be hugely useful. They’re even available in IOS now (as of 12.4(20)T). Here’s an example of when they’d be used:
Awhile ago a friend asked me for a write up on IOS Firewall/CBAC. At the time I hadn’t felt like writing about it as I don’t use it much, but I recently had to configure it, so I thought I may as well take a break from Juniper posts and do the article.
The IOS Firewall uses CBAC (Context-Based Access Control) to inspect traffic flows at the upper layers. CBAC will inspect the outgoing traffic while maintaining stateful intformation for each session. It will then open pinholes in the firewall/incoming ACL to allow appropriate traffic back in. Something I forgot to point out, CBAC can be very CPU intensive, your traffic. Keep that in mind before and do some testing before deploying it on your network. Here’s the topology:
We have our router running IOS firewall, its WAN connection is on Fa0/1 out to the internet, and its LAN connection is on Fa0/0, which connects to some servers and workstations. Let’s configure the firewall:
In this article we will configure GRE/IPSEC tunnels. These are used in cases where there is a desire to run routing protocols across a VPN connection. This article is useful for CCNP (ISCW) and CCSP studies.
First we will create our ISAKMP Policy, then we will create a key and associate it with a peer, next we build our Transform Set, then the ACL with traffic to be encrypted, followed by the Crypto Map and finally to the Tunnel interface configuration.
Here’s our ISAKMP Policy:
crypto isakmp policy 10 encr aes 256 authentication pre-share group 5
We set the encryption to an AES 256 bit key, use pre-shared authentication (keys) and Diffie-Hellman Group 5.
Next we create a key and associate it with a peer:
crypto isakmp key Sup3rS3cr3tK3y address 22.214.171.124
Now we build the Transform Set:
crypto ipsec transform-set secure_transform esp-aes esp-sha-hmac
Next we make our ACL:
ip access-list extended GRE_IPSEC_TRAFFIC permit gre host 126.96.36.199 host 188.8.131.52
This is catching GRE traffic from 184.108.40.206 (us, the source) to 220.127.116.11 (our peer, the destination).