Review, Part 2

4/15/2009

Final Exam

The final exam will be posted by 6pm on Wednesday, April 29, 2009 and you have a week to find three hours to work on it. Use any resource, including asking me questions if you're not sure; don't hesitate to ask me questions. Please let me know if it looks like it will take you more than three hours since that means you're making it harder than I intended. 445-9385

Project

Review

Now, on to the review! Unless you have questions ...

Performance

Latency

Practical Considerations

Troubleshooting Tools

Layer 2 header for 802.1Q

802.1Q VLANs

VLAN Facts of Life

  1. 802.1Q adds 4 bytes to Ethernet packets between the Layer 2 (Ethernet) header and the Layer 3 leader, increasing the maximum packet size from 1518 to 1522 bytes; 3 bits are for the 802.1p Ethernet class of service and 12 bits are for the 802.1Q VLAN ID.
  2. A VLAN, by definition, provides broadcast containment. Broadcasts (Windows browser elections, Bonjour) are contained within the VLAN.

VLAN Facts of Life

  1. Your IP address determines your IP subnet (of course). Your IP subnet uniquely determines your 802.1Q VLAN. Each VLAN can have several subnets, but each subnet has one and only one VLAN. If the VLAN on your switch port doesn't match your IP address subnet, you can't communicate on the network (except at Layer 2, but the user reports no network connectivity).
  2. For traffic to travel between VLANs, it must go to the router port defined for that VLAN (your gateway). In the simplest case, it then goes through the routing engine and out the router port for the destination VLAN. (It could also go from the routing engine on one router to the routing engine on another router, and then out the router port for the destination VLAN.) Each router knows what subnets match the VLANs it manages, and it knows what router to send packets for the VLANs it doesn't manage.

VLAN Scalability for Users

  1. You can put every user port in a VLAN manually. This isn't so bad as long as departments (or functional groupings) don't change too much.
  2. You define policy (from RFC 3580) to change as needed, but the default policy matches what you would set above.

VLAN Scalability for Uplinks

  1. You can add every VLAN to every switch uplink port (called a trunk port if it trunks more than one VLAN through; all traffic must be VLAN-tagged at this point, or else it will get the PVID (port VLAN ID) from the trunk port) that it might need to traverse to get to other users in this VLAN (what about user mobility???), or ...
  2. You can turn on GVRP and that will dynamically add to every trunk port (that has GVRP enabled) every VLAN that it "hears" so that VLAN traffic can go wherever needed. Not supported by Cisco.

VLAN Scalability at UNC

We use Door #2 wherever possible!

Quality

QoS

QoS

QoS Compared

When to use QoS

Where to use QoS

DNS

DNS Records

DNS Troubleshooting

DHCP

Security

Routing

Routing

Routing: MPLS

Routing: OSPF