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...
Cisco ASA 5500 – Performing NAT for Two (or More) internal IP’s to a Spare Public IP
KB ID 0001057 Problem I was in the PIX/ASA area at EE last night, and a poster asked if they could perform NAT on a couple of internal IP addresses to a spare public IP that they had. I had done this for a client some time last year when I performed and upgrade from 8.2. Anyone who has ever done a large upgrade on an ASA to the ‘new’ NAT system, will appreciate this is usually the area where the upgrade has a problem. So...
Cisco ASA 5500 – Sub Interfaces and VLANS
KB ID 0001085 Problem You can take the physical interface of a Cisco ASA firewall, (or an ether channel) and split it down into further sub-interfaces. This way you can set multiple VLANs to use this interface as a gateway at the same time whilst still separating the traffic. In this scenario I’m going to have two VLANs, one for my wired clients, and one for a ‘Guest WiFi’ that I’m setting up. I want the guest...
CentOS 7 – No Network Connection
KB ID 0001047 Problem A while ago I spun up a CentOS server in VMware Workstation, and I could not get it connected to the network, I was in a bit of a hurry, so I blew it away and just built a new server with CentOS 6. This week I’ve been using VirtualBox and spun up a new CentOS 7 server and had the same problem. Solution 1. Quite why CentOS 7 does this I’m not sure, My NIC is called enp0s3 (run ‘ip addr’ to...