Tag Archives: written

Cisco – Migrating from STP to RSTP

CCIE

A frequent CCIE-level written exam topic is STP (PVST+) to RSTP (Rapid-PVST) migrations. This post covers the high points you should be aware of.

Some Quick Notes

  • BackboneFast and UplinkFast are no longer necessary in RSTP environments as the equivalent advantages are built-in to RSTP
  • BPDUs are version 2 in RSTP which is compatible with version 0
  • All ports now send BPDUs and they act as a keepalive mechanism
  • The new port roles are designated, root, alternate, and backup
  • The new port states are forwarding, discarding, and learning
  • The new port types are shared, edge (PortFast), and P2P
  • When an RSTP port receives a legacy BPDU, it reverts back to compatible behavior and performance enhancement benefits are lost
  • BackboneFast is configured on all switches in order to function in STP and UplinkFast is configured on access layer devices

Migrating

  • You are not forced into removing the BackboneFast and UplinkFast commands – if they are left in place, they do not impact the operation of RSTP
  • Removing the Uplinkfast command impacts the bridge priority and port cost values, so be sure you consider this
  • CatOS (FLASHBACK!) does not permit the BackboneFast command within RSTP so you must remove it in that legacy case
  • Plan a phased migration and use a maintenance window as traffic flows can be impacted
  • The configuration of the features such as PortFast, BPDUguard, BPDUfilter, root guard, and loopguard are applicable in rapid-PVST+ mode also

400-101 CCIE R&S Written – Free Resources – UDP Operations

UDP

If a TCP session is like a phone call – then a UDP transmission is like a postcard! Here are the free study resources around UDP!

1.1.f Explain UDP operations
1.1.f [i] Starvation
1.1.f [ii] Latency
1.1.f [iii] RTP/RTCP concepts

The UDP Protocol

UDP Broadcast Flooding

Defending Against Distributed DoS Attacks

IP SLA Configuration Guide

RTP

CCIERS

400-101 CCIE R&S Written – Free Resources – TCP Operations

TCP

Here are the free resources surrounding the Explain TCP Operations section of the CCIE R&S Written version 5.1 exam.

1.1.e Explain TCP Operations

  • 1.1.e.i     IPv4 and IPv6 PMTU
  • 1.1.e.ii    MSS
  • 1.1.e. iii  Latency
  • 1.1.e. iv  Windowing
  • 1.1.e.v    Bandwidth delay product
  • 1.1.e.vi   Global synchronization
  • 1.1.e       Options

TCP Performance – The Internet Protocol Journal – Volume 3, No. 2

Resolve IP Fragmentation, MTU, MSS, and PMTUD Issues with GRE and IPSEC

IP Application Services Configuration Guide, Cisco IOS Release 15M&T

IPv6 Addressing and Basic Connectivity Configuration Guide, Cisco IOS Release 15M&T

IP SLAs Configuration Guide, Cisco IOS Release 15M&T

TCP Options

TCP Global Synchronization 

TCP/IP Illustrated, Volume 1

CCIERS