Tag: router

About

In simple layman terms, a router is a device that determines the proper path for data to travel between different networks. They connect networks together; a LAN to a WAN for example, to access the Internet. Some units, like the Cisco 1800 (pictured), are available in both wired and wireless models.

Routers intended for ISP and major enterprise connectivity will almost invariably exchange routing information with the Border Gateway Protocol. RFC 4098 [4] defines several types of BGP-speaking routers:

  • Provider Edge Router: Placed at the edge of an ISP network, it speaks external BGP (eBGP) to a BGP speaker in another provider or large enterprise Autonomous System (AS).
  • Subscriber Edge Router: Located at the edge of the subscriber's network, it speaks eBGP to its provider's AS(s). It belongs to an end user (enterprise) organization.
  • Inter-provider Border Router: Interconnecting ISPs, this is a BGP speaking router that maintains BGP sessions with other BGP speaking routers in other providers' ASes.
  • Core router: A router that resides within the middle or backbone of the network rather than at its periphery.

Within an ISP: Internal to the provider's AS, such a router speaks internal BGP (iBGP) to that provider's edge routers, other intra-provider core routers, or the provider's inter-provider border routers.

"Internet backbone:" The Internet does not have a clearly identifiable backbone, as did its predecessors. See default-free zone (DFZ). Nevertheless, it is the major ISPs' routers that make up what many would consider the core. These ISPs operate all four types of the BGP-speaking routers described here. In ISP usage, a "core" router is internal to an ISP, and used to interconnect its edge and border routers. Core routers may also have specialized functions in virtual private networks based on a combination of BGP and Multi-Protocol Label Switching (MPLS).

From en.wikipedia.org/wiki/Router#Routers_for_Internet_connectivity_and_internal_use

 

Make SSH connections with PHP

Not everyone knows about PHP's capabilities of making SSH connections and executing remote commands, but it can be very useful. I've been using it a lot in PHP CLI applications that I run from cronjobs, but initially it was a pain to get it to work. The PHP manual on Secure Shell2 Functions is not very practice or thorough for that matter, so I would like to share my knowledge in this how to, to make it a little less time consuming setting this up.