Category Archives: Routing

Static routes, routing protocols, etc.

OSPF Visualizer

While reading the OSPF chapter in the Cisco CCNP ROUTE learning guide, I was interested in how to visualize an OSPF area. Since every router in the same area has a complete view of all routers and networks, it should be easy to draw a map. So, I searched through the web for this kind of OSPF plotter and found two different approaches. While none of them worked out of the box, I was able to run one of them with an additional software router (Quagga) inside my OSPF area which finally drew a map. Yeah. Here we go:

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Policy Based Routing on a Cisco ASA

Cisco ASA 9.4 (and later) is now supporting Policy Based Routing. Yeah. Great news, since many customers are requesting something like “HTTP traffic to the left – VoIP traffic to the right”. Coming with a new Cisco ASA 5506-X I was happy to try the policy based routing feature.

The configuration steps through the ASDM GUI are not easy and full of errors so I am trying to give some hints within this blog post.

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Policy Based Forwarding on a Palo Alto with different Virtual Routers

This guide is a little bit different to my other Policy Based Forwarding blog post because it uses different virtual routers for both ISP connections. This is quite common to have a distinct default route for both providers. So, in order to route certain traffic, e.g., http/https, to another ISP connection, policy based forwarding is used.

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Policy-Based Routing on ScreenOS with different Virtual Routers

I already puslished a blog post concerning policy-based routing on a Juniper firewall within the same virtual router (VR). For some reasons, I was not able to configure PBR correctly when using multiple VRs. Now it works. ;) So, here are the required steps:

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Policy Routing on a FortiGate Firewall

This is a small example on how to configure policy routes (also known as policy-based forwarding or policy-based routing) on a Fortinet firewall, which is really simple at all. Only one single configuration page and you’re done. ;)

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IPv6 through IPv4 VPN Tunnel with Juniper SSGs

The most common transition method for IPv6 (that is: how to enable IPv6 on a network that does not have a native IPv6 connection to the Internet) is a “6in4” tunnel. Even other tunneling methods such as Teredo or SixXS are found on different literatures. However, another method that is not often explained is to tunnel the IPv6 packets through a VPN connection. For example, if the main office has a native IPv6 connection to the Internet, as well as VPN connections to its remote offices, it is easy to bring IPv6 subnets to these stations.

Here is how I did it with some Juniper SSG firewalls:

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Advanced Tracerouting

A commonly misunderstanding of traceroute is that it fully relies on ping. “If I block ping at my firewall, no one can use traceroute to reveal my internal routing path”. Unfortunately this is not true. If traceroute is used with TCP SYN packets on permitted TCP/UDP ports, all intermediary firewalls will handle the IP packets with TTL = 0 corresponding to the RFCs and will reply with an ICMP time exceeded packet to the source.

In this post I am listing an example that uses traceroute with TCP port 25 (SMTP) to traverse a firewall. A sample pcap file can be downloaded while some Wireshark screenshots show a few details.

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OSPF for IPv4 Test Lab: Cisco Router & ASA, Juniper SSG & Palo Alto

I tested OSPF for IPv4 in my lab: I configured OSPF inside a single broadcast domain with five devices: 2x Cisco Router, Cisco ASA, Juniper SSG, and Palo Alto PA. It works perfectly though these are a few different vendors.

I will show my lab and will list all the configuration commands/screenshots I used on the devices. I won’t go into detail but maybe these listings help for a basic understanding of the OSPF processes on these devices.

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Juniper ScreenOS Firewall autocorrects Route Entries

I was a bit confused today as I saw a “wrong” route entry in the config of an SSG firewall. The route had not the correct “network/netmask” notation but a “host-address/netmask-of-the-network” notation. However, the SSG autocorrected this false route entry to the correct subnet id in its routing table.

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Basic ISP Load Balancing with a Cisco Router

“We have two independent DSL connections to the Internet and want to share the bandwidth for our users.” This was the basic requirement for a load balancing solution at the customer’s site. After searching a while for dedicated load balancers and thinking about a Do-It-Yourself Linux router solution, I used an old Cisco router (type 2621, about 40,- € on eBay at the time of writing) with two default routes, each pointing to one of the ISP routers. That fits. ;)

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Policy-Based Routing (PBR) on a Juniper ScreenOS Firewall

Here comes an example on how to configure policy-based routing (PBR) on a Juniper ScreenOS firewall. The requirement at the customers site was to forward all http and https connections through a cheap but fast DSL Internet connection while the business relevant applications (mail, VoIP, ftp, …) should rely on the reliable ISP connection with static IPv4 addresses. I am showing the five relevant menus to configure PBR on the ScreenOS GUI.

[UPDATE] I later on wrote an article with policy-based routing with two different virtual routers. See it here.[/UPDATE]

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Policy Based Forwarding (PBF) on a Palo Alto Firewall

This is a small example on how to configure policy based forwarding (PBF) on a Palo Alto Networks firewall. The use case was to route all user generated http and https traffic through a cheap ADSL connection while all other business traffic is routed as normal through the better SDSL connection. Since I ran into two problems with this simple scenario, I am showing the solutions here.

[UPDATE] I also wrote an article about policy based forwarding with two different virtual routers on the Palo Alto firewall. See it here.[/UPDATE]

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