Comparing Layer 2 and Layer 3 Encapsulation

All rights re Layer 2 and Layer 3 switches each make decisions about how to handle units of data, known as frames (Layer 2) and packets (Layer 3). A frame is a Layer 2 encapsulation, while a packet is a Layer 3 encapsulation. For example, Ethernet is used for a Layer 2 frame encapsulation, while IP is used for a Layer 3 packet encapsulation. Layer 2 and Layer 3 switches both read the destination address (DA) field. Layer 2 uses the frame DA field to make switching...

Source Trees vs Shared Trees

Both source trees and shared trees are loop-free. Messages are replicated only where the tree branches. Members of multicast groups can join or leave at any time therefore, the distribution trees must be dynamically updated. When all the active receivers on a particular branch stop requesting the traffic for a particular multicast group, the routers prune that branch from the distribution tree and stop forwarding traffic down that branch. If one receiver on that branch becomes active and...

Security in the Multilayer Switched Network

Network security vulnerabilities include loss of privacy, data theft, impersonation, and loss of integrity. Cisco recommends tasks that you should complete to secure your switched network from attack. This topic introduces security in a multilayer switched network. r.cn, 2004, Cisco Systems, Inc. All rights reserved. You should implement a basic security configuration on every installed Cisco IOS device. The primary focus is to apply minimal security to mitigate user negligence in regards the...

Verifying the Modular QoS CLI Configuration

Switch show class-map class-map-name Switch show policy-map interface interface-spec Switch show policy-map max-pol-ipp5 Policy Map max-pol-ipp5 class ipp5 class ipp5 police flow 10000000 10000 conform-action set-prec-transmit 6 exceed-action policed-dscp-transmit trust precedence police 2000000000 2000000 2000000 co nform-action set-prec-transmit 6exceed-action policed-dscp-transmit 2004, Cisco Systems, Inc. All rights reserved. BCMSN v2.1 8-48 Verifying the Modular QoS CLI Configuration...

Example HSRP on Non Preempt Configured Router Coming Up

Router DSW111 is configured with a priority of 100. This priority is higher than the priority of the current active router DSW112 (172.16.11.112), which has a priority of 50. Note that router DSW111 is not configured with preempt. Only when a router is configured with preempt will a router with a higher priority immediately become the active router. After router DSW111 goes through the HSRP initialization states, it will come up as the standby router. DSWlll(config) interface vlan 11...

Troubleshooting CEF

Switch debug ip cef drops receive events prefix-ipc I table Displays debug information for CEF Switch debug ip cef ipc interface-ipc Displays debug information related to IPC in CEF 2004, Cisco Systems, Inc. All rights reserved. BCMSN v2.1 5-34 Use the debug ip cef EXEC commands for troubleshooting CEF. The syntax is as follows debug ip cef drops access-list receive access-list events access-list prefix-ipc access-list table access-list The arguments to the debug command include the following...

Issues in a Poorly Designed Network

Reduced support for services and solutions 2004, Cisco Systems, Inc. All rights reserved. BCMSN v2.1 1-37 A poorly designed network has increased support costs, reduced services and solutions that can be supported, and nonoptimal performance issues that most likely will affect end users directly. Here are some of the issues that stem from a poorly designed network Failure domains One of the most important reasons to implement an effective design is to reduce the impact of network problems...

Example HSRP on Preempt Configured Router Coming Up

DSW111 is configured with a priority of 100. This priority is higher than the priority of the active router DSW112 (172.16.11.112). DSW111 is also configured with preempt. Only when a router is configured with preempt will that router with a higher priority transition into the active state. At time-stamp Mar 1 00 16 43.099, the interface VLAN11 on DSW111 comes up and transitions into the listen state. At time-stamp Mar 1 00 16 43.295, DSW111 receives a hello message from the active router...

Ternary Content Addressable Memory Table

Matches only the important values (not all values) Matches based on three values 0, 1, or X (either) Masks used to wildcard some content fields 1 Mid > . h All 32 Bits of Smircc IP A ddreRE TCAM is a specialized piece of memory designed for rapid table lookups based on packets passing through the switch performed by the ACL engine. The result of the ACL engine lookup into the TCAM table determines how the switch handles a packet. For example, the packet might be permitted or denied. The TCAM...

RSTP Port States

Juniper Trunk Sample

All rights re RSTP provides rapid convergence following the failure or re-establishment of a switch, switch port, or link. An RSTP topology change will cause a transition in the appropriate switch ports to the forwarding state through explicit handshakes or a proposal and agreement process and synchronization. With RSTP, the role of a port is separated from the state of a port. For example, a designated port may be in the discarding state, even though this condition...

IGMP v3 Query Message Format

Croup address 5 QRV QQIC riurnheroUsurcealN 2004, Cisco Systems, Inc. All rights re IGMP version 3 IGMP v3 is the next step in the evolution of IGMP. IGMP v3 adds support for source filtering. This enables a multicast receiver host to signal to a router the groups from which it wants to receive multicast traffic and from which sources this traffic is expected. This membership information enables IOS software to forward traffic from only those sources from which receivers requested the traffic....

Layer 2 Marking 8021p CoS

Thnc-fi Hi amp Ljlsctl for C 0 8 2 1p User rinni1y Thnc-fi Hi amp Ljlsctl for C 0 8 2 1p User rinni1y 802.1 p User Priority field also called class of service CoS . Different types of traffic are assigned different CoS values. CoS 6 and 7 are reserved for network use. 2004, Cisco Systems, Inc. All rights re With a Layer 2 switching engine, Layer 2 QoS supports classification using Layer 2 destination MAC addresses, and VLANs and marking using Layer 2 CoS values on the ingress port or interface....

Displaying CEF Entries in the FIB

Switch show ip cef type alot port number detail Switch show ip cef ethernetO O 172.19.233.33 detail IP Distributed CEF with switching Table Version 1368O8 458OO routes, 8 unresolved routes O old, 8 new 458OO leaves, 2868 nodes. 1368O8 inserts, 91OO8 invalidations 1 load sharing elements, 2O8 bytes, 1 resets, 1 revisions of existing leaves refcounts 527343 leaf, 465638 node 172.19.233.33 32, version 7417, cached adjacency 172.19.233.33 0 packets. via 172.19.233.33, Ethernet0 0, 0 dependencies...