Host and Small Network Relaying Howard C. Berkowitz Chapter 6 Host and Small Network Relaying Howard C. Berkowitz 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

Host and Small Network Relaying Hosts can be passively aware of routing Simple default gateway More complex load sharing Can also act as routers Relay packets from host to host, or external routers. Relaying general concept that involves switching and routing. RIP-simple signaling mechanism for hosts to find the default gateway. 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

Workgroup Switching Switches Good tool to provide fast paths to local servers Reduce latency Network designer goal is to provide useful bandwidth. Do not want to provide more bandwidth than a server can use. Server should be free from waits for bandwidth, it should be full dup and Gb range. 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

Workgroup Switching Reasons to use switches VLANs Min bandwidth contention on servers 100mbps and full dup Provide fast inter-host paths when there is significant peer-to-peer operation. VLANs Broadcast and multicast isolation Some automation of moves and changes Cabling flexibility 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

Alternatives to Routers for Inter-subnet Communications Application Gateways Hosts do not need to communicate with one another Communicate with servers Application gateways are ideal in an office automation setting Products can have firewall as well as router functions. 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

Shared Access to Printer and a WAN Gateway. Cached Access to a Printer and a WAN Gateway Lookups normally sent to data center can be done on a local cache Small switch could be useful for speeding access to critical cache servers. 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

Local Mail Gateway Switch allows concurrent transfers between one client and the cache. Other client transfers to external gateway and the printer. 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

Alternatives to Routers for Inter-subnet Communications Multiple Interface Servers Connect a server to multiple use LANs and interfaces. 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

Alternatives to Routers for Inter-subnet Communications VLAN-Aware Servers Multiple interface method to bring VLANs into the server. VLAN aware server card Server will appear to be on each VLAN No router required 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

Hosts’ Involvement in Routing Basic Router Location Host must be able to find default gateway. Hard-Coded Default GW Proxy Address Resolution Protocol (ARP) Router Discover protocols IDRP Passive RIP-simply to find default gateway 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

Hosts’ Involvement in Routing Passive RIP For Router Location and other functions RIP often runs on non-routing hosts Done to find default gateway Load Sharing-spreads load over shared resources Load balancing-uses more overhead 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

Hosts’ Involvement in Routing Interactions with Microsoft RAS 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

RIP Workload and Convergence RIP Traffic Oldest protocol that is still used Convergence Time Only keep track of routes that it is currently using. Sum of basic failure detection and the time to get an update. 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

When and How to Use Routing in Small Networks RIP is a simple choice for many networks-not always the best choice. Static routing could be a better choice. RIP is adequate for router discovery and very simple topologies. 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

When and How to Use Routing in Small Networks Hub-and-Spoke Topology All servers at the data center Spoke sites only need to know how to reach the data center. Overhead For small networks overhead for RIP is minimal 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

When and How to Use Routing in Small Networks Distributed Topology with Equal Cost Paths Quasi-static routing can be practical when dealing with a few nodes More complex topologies need dynamic routing A single alternate path almost always increases availability. The more alternate path topology approaches full mesh, the more overhead it takes to converge. Holddown timer keeps being reset. 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

When and How to Use Routing in Small Networks Distributed Topology with Unequal Cost Paths RIP is unaware of bandwidth on links. Only minimizes the number of links taken. OSPF or EIGRP works well Static can work if topology is not to complex. 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

RIP Version 2 Added features but did not change limitations of RIPv1 VLSM and CIDR Send updates as multicasts rather than broadcasts. 7/15/2019 Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing