Stub router
A Stub router, One-armed router or router on a stick is
a router that routes traffic between virtual
local area networks (VLANs). It has only a single Ethernet
NIC that is part of two or more Virtual
LANs, enabling them to be joined.A VLAN allows multiple virtual LANs to coexist on the same physical LAN. This means that two machines attached to the same switch cannot send Ethernet frames to each other even though they pass over the same wires. If they need to communicate, then a router must be placed between the two VLANs to forward packets, just as if the two LANs were physically isolated. The only difference is that the router in question may contain only a single Ethernet NIC that is part of both VLANs. Hence, "one-armed".
Autonomous System
Within the Internet,
an Autonomous System (AS) is a collection of connected Internet
Protocol (IP) routing prefixes under the control of one or more network
operators that presents a common, clearly defined routing
policy to the Internet.[1]Originally the definition required control by a single entity, typically an Internet service provider or a very large organization with independent connections to multiple networks, that adhere to a single and clearly defined routing policy, as originally defined in RFC 1771.[2] The newer definition in RFC 1930 came into use because multiple organizations can run BGP using private AS numbers to an ISP that connects all those organizations to the Internet. Even though there may be multiple Autonomous Systems supported by the ISP, the Internet only sees the routing policy of the ISP. That ISP must have an officially registered Autonomous System Number (ASN).
A unique ASN is allocated to each AS for use in BGP routing. AS numbers are important because the ASN uniquely identifies each network on the Internet.
Until 2007, AS numbers were defined as 16-bit integers, which allowed for a maximum of 65536 assignments. The Internet Assigned Numbers Authority (IANA) has designated AS numbers 64512 through 65534 to be used for private purposes.[3] ASNs 64496-64511 are reserved for use in documentation and sample code.[4] The ASNs 0 and 65535 are reserved; ASN 0 may be used to identify non-routed networks. All other ASNs are subject to assignment by IANA. RFC 4893 introduced 32-bit AS numbers, which IANA has begun to allocate. These numbers are written either as simple integers, or in the form x.y, where x and y are 16-bit numbers. Numbers of the form 0.y are exactly the old 16-bit AS numbers, 1.y numbers and 65535.65535 are reserved, and the remainder of the space is available for allocation.] The accepted textual representation of Autonomous System Numbers is defined in RFC 5396.
The number of unique autonomous networks in the routing system of the Internet exceeded 5000 in 1999, 30000 in late 2008, and 35000 in mid 2010
Protocols in Autonomous System
1)
IGP (Interior
gateway protocol)
IGP is used to communicate within onc ISP or within
autonomous system
Different types of igp are
- a) RIP
- b) OSPF
- c) IGRP
2)
EGP (Exterior gateway
protocol)
This protocol is
used to communicate between to different autonomous system or between to
different ISPs
Following points
should be keep in mind while doing routing
- · Destination
- · Directly connected networks / services from which to learn
- · Possible routes
- · Best route
In privilege mode type following command
to check information sharing between routers
Debug ip rip
No debug ip rip command to undo above command
Topics of Next lecture
·
Distance vector
protocol
·
Link state
