Category Archives: Computer Networking

This category contains any networking related materials.

FreeBSD firewall with Strongswan building site to site vpn tunnel – sample

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I recently has upgraded the FreeBSD version to 13 and found that the IPSec site to site between FreeBSD 13 to Juniper SRX is not working anymore. Strongswan is ditching the ipsec.conf and move to swanctl.conf. If we are moving to the vici, this requires some effort to translate the config.

I have attached the quick and dirty sample to build a Policy based site to site IPSec vpn with Strongswan. Enhancement is required for production.
The sample is suitable for the following:
– policy based VPN
– using PSK.
– source vpn termination point is NATTed and behind a internet gateway.
– dynamic public IP address for source vpn termination point.
– dynamic destination IP address for the remote IPSec VPN termination point. (required the DNS lookup for the source vpn termination point.)
– multiple VPN termination points from the same source public IP address are allowed.

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Install FreeBSD into a headless machine using serial console cable

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I have received a checkpoint firewall that has 2GB of ram and running a D525 CPU. I was thinking what can i do with it. Then i start doing the project that has been in my mind for a long time, which is to use FreeBSD as a firewall.

There is a main purpose of using FreeBSD is I want to use it as a bandwidth control device. Therefore, I start setting up the FreeBSD firewall before I get into the bandwidth control. Long story short, let s dive into the headless FreeBSD installation.

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Convert Cisco FTD to ASA firmware

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The Cisco firewall comes with the FTD firmware by default, and there are several reasons of using the ASA firmware on this Cisco new firewall. I have attached the steps below to let the Cisco firewall to run the ASA firmware by re-imaging it.

This is the same way to change from ASA firmware to FTD firmware.

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Hping3 – Linux的仿真數據包泛洪攻擊

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在針對防火牆對DoS和會話限制能力測試時，Linux 中有一個名為hping3的程序可以產生仿真數據包泛洪攻擊。它可以產生少量的數據包氾濫，同時仍然保持至少50％的CPU可用於管理。

如果我們需要測試SYNC泛洪的會話限製或閾值限製到Web服務器端口80，我們可以使用下面的命令。

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Hping3 – Flooding simulation with Linux 

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When testing firewalls ability against the DoS and session limit, there is a program in Linux called hping3 to produce flooding with. It can generate a small amount of packet flood while still keeping at lease 50% of CPU free for management.
if we need to test a session limit or threshold limit for SYNC flood toward to a web server port 80, we could use the command below.

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IPv6 over IPv4 in SRX

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IPv6 is another up coming trend on the internet. Since most of the ISPs do not provide the IPv6 service, how do we enjoy or experience the IPv6 benefit??
There are some IPv6 brokers on the internet that we can use IPv6 service over the existing IPv4 service. Some of the brokers are Hurricane Electric, Hinet, and etc….
There are some sample setup guide are already included in their website already, but their guide makes the SRX to route the IPv6 packets without policy restrictions capability. So I will attach mine as a reference for using IPv6 in flow mode.
SRX-IPIP
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MPLS VPN – option C – using bgp label exchange with cisco and Junos -part 1

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It has been a while since I have done any labs after getting a new job. This time, I will be building a NNI option C using both Cisco IOS and Juniper MX. The reason I write this is because I do not find many resources on the internet about the inter AS connection using 2 different software at the same time. Hope this can be useful for anyone who is having the same struggle as i do.
(the AS# below are randomly picked!!)
lab-testing-mpls
Based on the lab diagram (dont feel like copping it up), as the internal VPN service is already running and the intra AS is running OSPF and LDP for MPLS, I will be connecting AS5052 (the green aren in middle) and AS7077 (the orange area at the bottom) together over NNIs to extend the MPLS VPN services.
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Cisco ASA – Site to Site IPSec VPN with dynamic IP address

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Setting up a policy based site to site IPSec VPN tunnel with static IP address is quite stright forward in Cisco ASA, but what if one of the end point is using dymanic IP address?
In this lab, I will be using 2 virtual ASA (9.6(2)) to create a site to site IPSec VPN tunnel, as well as setting up Cisco VPN client in one of the ASA with static IP address.
The ASA-F14 is the one with static IP address, and the ASA-F16 is using dynamic IP address.
20161221-mpls-2vrfs
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MPLS VPN – routes sharing between 2 different VRFs across the MPLS network

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The beaut of MPLS VPN is to have multi tenants running over the same MPLS core network and each tenant are prevented to access other tenants networks. But what if the 2 different tenants want to connect to each other?
In the lab below, we have 2 different tenants and they are 1120020010 (RT:200010) in Router 12 and 1030010010 (RT:100010) in Router 03. By default, the ASAs connected to these VRFs cannot communicate since they are in 2 different VRF network. In this case, I will be using Cisco IOS and Juniper MX to let 2 different VRFs to connect together.
20161221-mpls-2vrfs
We could check the existing configuration and the route table in Router 03 and Router 12
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Cisco ASA – simple 1 to 1 NAT and firewall policy setup

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For those who had been working with Cisco routers, setting up a Cisco ASA stateful policy is as simple as setting up an ACL.  By default, ASA would drop any TCP connection that doesn’t have a session record created with a sync packet. In that case user doesn’t require to a setup ACL for return traffic like working with routers.
In this example, we have 192.168.104.250/32 as the server in the DMZ and have the have NAT 1 to 1 incoming traffic mapping applied to allow internet user accessing the http service only.
The IP address of the firewall is 10.50.2.10/29, and we will assign the mapping of the server to another external IP address of 10.50.2.11
20161215-vasa-lab-nat Continue reading →