The looking glass service

Many internet agents offer (ISPs, IXPs, etc) what it's called the looking glass service . Only in this web site a full list of 1150 looking glass services are offered: http://www.bgplookingglass.com.

Looking glass services are a great way to understand if a target is up and how to reach it.

It's important to note that the Looking Glass service can be configured on Juniper, Cisco (IOS o IOS-XR), Extreme (NetIron), Quagga, BIRD, OpenBGPd, Vyatta/VyOS/EdgeOS, or FRRouting routers.

OTOH, it's necessary to install a Looking Glass client in a web server in order to be able to use the service. There exist a number of Looking Glass (often called LG) service software packages that can be installed in a web server. . In Ubuntu/Debian we can find:

# apt-cache search looking | grep glass
rancid-cgi - looking glass CGI based on rancid tools

However, the only documentation found about this package is this website, which means it's not widely used.

We al have MRLG (See http://mrlg.op-sec.us/), but it seems quite old...

Nevertheless, the typical LG software used is the standard version of Looking Glass obtained from Version6.net. A good source explaining how to install it in a CentOS distro is: http://amar-linux.blogspot.com/2013/06/setting-up-bgp-looking-glass-centos-6.html. It can also be found in its github reporsitory: https://github.com/version6net/lg.

All of them are services developed in Perl, however we can find other solutions developed in PHP, IE (https://github.com/respawner/looking-glass ...which is fully documented in https://looking-glass.readthedocs.io.

HOW DOES IT WORK

For the normal functioning of the Looking Glass service it's necessary to have access to router's ports 2601 and 2605. The software generally connects to these ports via telnet. Generally credentials for this telnet are stored in a config file and the LG software simply connects via telnet to the router and sends BGP commands, returning the output to the web service. The typical BGP commands are like "sh ip bgp".

Therefore it's necessary to open 2601 and 2605 ports in the firewalls before the LG service to work properly. It will also be necessary to have a working NGINX or Apache Web server. Finally the appropiate libraries will have to be installed (depending on each solution).

On the other hand the router will have to be prepared to wait allow BGP commands remotely. For instance configuration for a Juniper OS (at least for the PHP solution previously mentioned) is the following:https://looking-glass.readthedocs.io/en/latest/juniper/. A restricted user in the router is recommended for the telnet connection and BGP command execution.