Cisco ASA 5500 – Deny a Single IP Address External Access
KB ID 0000743 Problem This got asked on Experts Exchange today, the poster specifically asked for an ASDM solution, so here goes. However I will also do the commands as well. Solution Block an IP via ASDM 1. Connect to the ASDM > Configuration > Firewall > Add ‘Network Object’. Note: You could create a Network Object Group, then add a Network Object to that group. This is handy if there are liable to be more IP...
Cisco ASA 5500 Allowing Tracert
KB ID 0000753 Problem I’d always assumed that as Tracert uses ICMP, and that simply adding ICMP inspection on the ASA would let Tracert commands work. A client of mine is having some comms problems and wanted to test comms from his remote DR site, he had enabled time-exceeded and unreachable on the ASA (for inbound traffic) and that had worked. I checked the default inspection map and found inspect ICMP was there? As it turns...
ASA TFTP Error – (Cannot allocate memory)
KB ID 0000787 Problem I updated my ASA to version 9.1(1) tonight, that went well, but when I tried to update the ASDM image to version 7.1(1)-52 this happened; Accessing tftp://10.254.254.109/asdm-711-52.bin…!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!...
Cisco Firewall (ASA/PIX) – Granting Access to an FTP Server
KB ID 0000772 Problem If you have an FTP server, simply allowing the FTP traffic to it wont work. FTP (in both active and passive mode) uses some random high ports that would normally be blocked on the firewall. So by actively inspecting FTP the firewall will know what ports to open and close. Solution How you ‘allow’ access to the FTP server will depend on weather you have a public IP address spare or not, if you only...
Boot Cisco ASA From TFTP (Upgrade from ROMMON)
KB ID 0000792 Problem If your firewall wont boot, either because the OS is corrupt, or you have a faulty flash memory. You can get up and running by booting the device from a TFTP server instead. Solution Before you start make sure you have your TFTP server running and the operating system in its root folder. Install and Use a TFTP Server 1. Power on the firewall, during the boot phase press ESC to boot to ROMMOM mode. 2. The...
Cisco ASA 5500 – Configuring PPPoE
KB ID 0000831 Problem Until very recently I’d never had to configure PPPoE. Most of my clients in that sort of connection speed range have ADSL with a router provided by their ISP. A Router that connects via PPPoA usually. Here in the UK the main ISP’s (BT and Virgin) are busy rolling out FTTC connections that terminate with a ‘modem’ that presents an RJ45 socket. So without the need for a router, you can get...
Cisco ASA – Find Out VPN Tunnel Uptime
KB ID 0000863 Problem I needed to get the Uptime/Duration of a particular VPN tunnel this week. It was for a client with multiple VPN tunnels that was having problems with just one. Solution Option 1 via Command Line 1. Connect to to the firewall > Go to enable mode and use the following command, replace 123.123.123.123 with the IP of your VPN endpoint. PetesASA> PetesASA> enable Password: ******** PetesASA# show...
Cisco ASA 5505 Routing Between Two (Internal) VLANS
KB ID 0000869 Problem I had to set this up for a client this week, I’ve setup a DMZ on a 5505 before and I’ve setup other VLANs to do other jobs, e.g. visitor Internet access. But this client needed a secondary VLAN setting up for IP Phones. In addition I needed to route traffic between both the internal VLANs. I did an internet search and tried to find some configs I could reverse engineer, the few I found were old (Pre version 8.3)...
Packet-Tracer Fails Subtype: rpf-check Result: DROP
KB ID 000904 Problem I love packet-tracer, I use it a lot, especially when I’ve been told that the firewall I’ve installed is stopping a particular port. I had set up a simple port forward the other day, and when I went to check it with packet-tracer this happened. Petes-ASA# packet-tracer input outside tcp 123.123.123.123 443 192.168.1.10 443 <——-Output removed——–> Phase: 7 Type: NAT...
Cisco ASA – I Cannot Ping External Addresses? (Troubleshooting ICMP)
KB ID 0000914 Problem Considering we use ICMP to test connectivity, the fact that it is not a stateful protocol can be a major pain! Last week one of my colleagues rang me up and said, “Can you jump on this firewall, I’ve got no comms, and I cant ping external IP addresses. I can ping the internet from the firewall and I can ping internal IP addresses form the firewall”. Solution 1. Before we start, lets get the basics...