Routing

RIPv2:

Legacy, Link State is perferred
Periodic updates - 30s
Invalid timer - 180s
- After a route has not been heard from for 6 consecutive updates
Holddown timer - 180s
- After a route has changed metrics, no more updates are accepted
Flush Timer - 240s
- The between when a route becomes invalid and its removal from the routing table
Metric - hop count
- Range from 1-15, 16 being invalid
v2 is classless
Uses IP/UDP at its transport
- Port 250
Split Horizon
- Information about a route should never go back in the direction that it was received
Poison Reverse
- A means of ensuring a split horizon, the routes DOES advertise a route back to the router from which it was learned. BUT it sets the metric to 16
- Prevents routing loops

Used mainly in service provider networks
Adjacencies are all directly connected routers (neighboring)
Not as reliant on timers as RIPv2 but does maintain some to insure integrity
- Hello interval - 10s
- Hello multiplier - 3
- Holdtime = interval * multiplier = 30s
  - After 3 missed hellos a router tears down the adjaceny with the missing neighbor
Metric default is 10, configurable per interface
- Max is 1023, the maximum per interface metric 64(2^6)
- Metric-style allows a maximum metric of 16777214(2^24)
Every multi-access netowrk has a DR
- Becomes adjacent to all other routers on multi-access network
- Prevents all routers from forming mesh adjacencies
- Elected through voting, priority can be changed to determin ahead of time who will be DR and BDR
Does not use IP, uses Connectionless Newtork Services (CLNS)
- Layer 3 protocol, analogous to IP
- Each router needs to be configured with some basic CLNS settings
  - Network Entity Title (NET) one such address globally configured and it must be unique across the entire netowrk
IS type is a way of creating a heirarchical routing architecture
- Type 1 is used for routing within an area
- Type 2 is used for routing between areas
Type 1 routers only from adjacencies with other Type 1 routers and Type 1-2 routers
Type 2 routers only form adjacencies with other Type 2 routers and Type 1-2 routers

Combination of distance vector and link state methods
- Counts hops as the length of the path
- Sends updates on topology changes, like a link state protocol
BGP uses TCP as the transport protocol
- Port 179
- A pair of BGP peers forms a TCP connection between one another to exchange routing information
Used for intra (iBGP) and inter (eBGP) Autonomous System (AS) route exchanges
AS is contigous network that is controlled by one entity
- PTD’s network is 1 AS
Each AS is represented by an Autonomous System Number (ASN) assigned by ARIN
- PTD’s ASN is 3737
ASN is an important part of any BGP configuration
BGP Synchronization is generally disabled in a network
iBGP is fully meshed
Ultimate goal is to have all BGP routers agree on what is the best path for any BGP route
- If this does not occur, routing loops will happen
PTD sends our upstream Providers only our internal customer routes while we receive full routes from each peer
BGP has no load balancing

Route learned via one protocol does not automatically get learned/propagated by another protocol runnong on the same router
Route redistribtuion is the process of taking the routes learned via one protocol and forcing another routing protocol to send those routes to its peers in effect “redistributing” them
Should be filtered in some way to avoid looping
RIP is redistributed into IS-IS and vice-versa
Route-maps are used to filter the redistribtuion
PTD does not redistribute BGP

Multimode (MM)
Single mode (SM)
PTD normally uses multimode fiber for connections between devices inside a building, single mode fiber for connections between devices in different buildings
Simplex is usually in a yellow jacket, means only one fiber in the jumper
Multimode tend to have an orange jacket. Consisted of two fibers used for transmition and receiving