Routing is a combination of Distance Vector and Link State routing. An example of the use of this algorithm is EIGRP.
1. Enhanced Interior Gateway Routing Protocol (EIGRP)
EIGRP is a routing protocol created by CISCO. EIGRP is a routing protocol with a hybrid algorithm. EIGRP uses several terminologies, namely:
- Successor: a term used for the path used to forward data packets.
- Feasible Successor: the term used for the path that will be used to forward data if the successor is damaged.
- Neighbor table: a term used for a table containing addresses and interfaces for accessing the neighboring router.
- Topology table: a term used for a table that contains all the destinations of the surrounding routers.
- Reliable transport protocol: EIGRP can guarantee the order of data delivery.
EIGRP devices exchange hello packets to determine their surroundings. At high bandwidths, routers exchange information every 5 seconds, and every 60 seconds at lower bandwidths.
Extension of distance vector routing protocol. Combination of distance vector and link-state capabilities. Diffused Update Algorithm (DUAL) is used to calculate the shortest distance. There is no broadcast of information but it is triggered when there is a topology change so it is faster.
Table 3. Comparison of RIP, OSPF, BGP
2. Conclusion
The main function of the network layer is addressing and routing, Routing is a function that is responsible for carrying data through a set of networks by choosing the best path for data to pass through. Routing tasks will be carried out by a network device called a Router. A router is a network computer that is tasked or functioned to connect two or more networks. The router's task is to forward data (IP Forward Function must be activated) using a routing protocol (Routing Algorithm). Data is regulated by the Routed Protocol. How to build a routing table can be done by Static Routing, Default Routing and Dynamic Routing. Dynamic routing is one type of routing, where the router learns and updates the routing table if there is a change. Learning is done by communicating between routers with certain protocols. The advantage of dynamic routing when compared to others is because the network is not a static system, what is meant here is that the network is dynamic, which means it changes - change this according to dynamic routing which will automatically adapt to network developments, network developments in general are very rapid. In contrast to static routing, where route changes occur slowly, dynamic routing is different because there are periodic network condition updates and responses to link changes that occur.
3. QUESTIONS
- What do you know about dynamic routing and its concepts?
- Explain the advantages of dynamic routing!
- Briefly explain what is meant by distance vector routing protocol!
- Mention and explain the terminology in EIGRP!
- Compare from OSPF, BGP, RIP protocols!
Understanding Border Gateway Protocol (BGP)
BGP is a router for external networks. BGP is used to avoid routing loops on the internet network.
The BGP standard uses RFC 1771 which contains information about BGP version 4.
1. BGP concepts and terminology
The concepts and terminology can be seen in Figure 6.4.
Figure 6.4 BGP Components
BGP Speaker : A router that supports BGP.
BGP Neighbor (pair): A pair of BGP routers that exchange information with each other. There are 2 types of neighbors:
- Internal (IBGP) neighbor : a BGP pair that uses the same AS.
- External (EBGP) neighbor : a BGP pair that uses different ASes.
BGP session: session of 2 BGPs that are currently connected
Traffic type:
- Local: local traffic to the AS o Transit: all traffic that is not local.
US Type:
- Stub: the part of the AS that is connected to only 1 connection with the AS.
- Multihomed: this section is connected to 2 or more AS, but does not forward transit traffic.
- Transit: this section is connected to 2 or more AS, and forwards local and transit packets.
US Number: 16 bit unique number
AS path: the path taken by routing with AS number
Routing Policy: rules that must be followed regarding how to forward packets.
Network Layer Reachability Information (NLRI): used to advertise routers.
Routes and Paths : routing table entries.
2. BGP Operations
The BGP neighbor, peer, makes a connection according to the manual configuration on the router device and creates a TCP path with port 179. The BGP speaker will send a 19 byte keepalive message to maintain connectivity (done every 60 seconds).
When BGP runs in the AS system, it processes IBGP routing information until it reaches administrative distance 200. When BGP runs between AS systems, it processes EBGP routing information until it reaches administrative distance 20. BGP routers that process IBGP traffic are called transit routers. Routers that are on the outside of the AS system and use EBGP will exchange information with ISP routers.
The increasing number of networks will result in an increasing number of routing tables on BGP routers. To overcome this, we can use: route reflector (RFC 2796) and Confederation (RFC 3065).
A reflector router will reduce the number of connections required by an AS. With a router (or two routers for redundancy) can be used as a reflector router (router duplication), so that the other router can be used as a peer.
Confederation is used for large-scale AS networks, and can create shortcuts so that internal routing on the AS will be easy to manage. Confederation can be run simultaneously with router reflectors.
Understanding Enhanced Interior Gateway Routing Protocol (EIGRP)
EIGRP is a routing protocol created by CISCO. EIGRP is a routing protocol with a hybrid algorithm.
EIGRP uses several terminologies, namely:
- Successor: a term used for the path used to forward data packets.
- Feasible Successor: the term used for the path that will be used to forward data if the successor is damaged.
- Neighbor table: a term used for a table containing addresses and interfaces for accessing the neighboring router.
- Topology table: a term used for a table that contains all the destinations of the surrounding routers.
- Reliable transport protocol: EIGRP can guarantee the order of data delivery.
EIGRP devices exchange hello packets to determine their surroundings. At high bandwidths, routers exchange information every 5 seconds, and every 60 seconds at lower bandwidths.
Understanding Open Shortest Path First (OSPF)
OSPF is a link state-based routing protocol, included in the Interior Gateway Protocol (IGP). Using the Dijkstra algorithm to calculate the shortest path first (SPF). Using cost as a routing metric. After the routers exchange information, a link state database will be formed on each router.
OSPF is probably the most widely used IGP. It uses the MD5 method for authentication between routers before receiving Link-state Advertisement (LSA). Since the OSPF crew has supported CIDR and VLSM, unlike RIP. Even for OSPFv3 already supports for IPv6.
Routers in the same broadcast domain will perform adjacencies to detect each other. Detection is done by listening for "Hello Packets". This is called 2 way state. OSPF routers send "Hello Packets" in unicast and multicast ways. Multicast addresses 224.0.0.5 and 224.0.0.6 are used by OSPF, so OSPF does not use TCP or UDP but IP protocol 89.
What is RIP (Routing Information Protocol)
Routing protocol that uses distance vector algorithm, namely BellmanFord algorithm. First introduced in 1969 and is the first routing algorithm on ARPANET.
The initial version of this routing protocol was created by Xerox Parc's PARC Universal Packet Internetworking under the name Gateway Internet Protocol. Later renamed to Router Information Protocol (RIP) which is part of Xerox network Services.
A version of RIP that supports IP technology is included in the BSD system as a routed daemon.
The RIP specification can be found in RFC 1058.
RIP is a routing protocol with a distance vector algorithm, which calculates the number of hops (hop count) as a routing metric. The maximum number of hops allowed is 15 hops. Each RIP router exchanges routing information every 30 seconds, via UDP port 520. To avoid routing loops, the split horizon with poison reverse technique is used. RIP is the easiest routing protocol to configure.
RIP has 3 versions, namely RIPv1, RIPv2, RIPng
- RIPv1 is defined in RFC 1058, which uses classful routing, does not use subnets. It does not support Variable Length Subnet Mask (VLSM).
- RIPv2 came around 1994, improving the capabilities of Classless Inter-Domain Routing. Defined in RFC 2453.
- RIPng is a RIP protocol for IPv6. It is defined in RFC 2080.