Force10 S4810 – Stacking Vs. VLT

Force10 VLT Implementation

Hasan Mansur


Cisco offers three solutions for eliminating STP. These comprise the stacking feature on 3750/2950 models, VSS on 6500s, and vPC on Nexus 5k/7k platforms. An important point to remember in comparison of these three methods is that in vPC, the control planes of the peer switches are separate, unlike Stacking/VSS where all switches are maintained by a single control plane.

Force10 Switches offer two solutions of this nature, which are discussed below.

  • Force10 switches, specifically S4810, offer a feature known as VLT (Virtual Link Trunking). VLT Is a Dual Active Control Plane implementation, of a Multi-System LAG. Thus, in operation, it is very similar to Cisco vPC.
  • VLT is beneficial in environments where the downstream devices like access switches need to build port channels/Link Aggregation groups across two separate upstream switches. The downstream switches view the VLT peers as a single logical chassis, thus allowing the LAG group to…

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Basic IPv6 RIPng config commands


Setup unicast routing on all routers: ipv6 unicast-routing

If desired no dns lookups: no ip domain-lookup

Configure all interfaces with the necessary ipv6 addresses: ipv6 address X:X:X:X::/128 (example)

If not allowed to use any global unicast ipv6 address, then simply enable ipv6 on the interface to generate the link-local ipv6 address : ipv6 enable

Next you setup an ipv6 NAME : ipv6 router rip CISCOIPV6

Exit out of the config-rtr mode and then activate RIPng on all interfaces: ipv6 rip CISCOIPV6 enable .. This command is used instead of the network command n RIP, advertising the network on the interfaces and sending out RIP packets out the configured interfaces

Check config with : show ipv6 route

Ping all ipv6 adds to ensure conectivity is established

You can also ping the link-local ipv6 addresses but you need to specify their output interfaces:


show ipv6 interface brief – will show brief overview of ips or ipv6 addresses, including link-local, configured on interfaces

VTP v3 tidbit

Interesting bit with VTPv3. Error received while attempting to create a VLAN:

VTP VLAN configuration not allowed when device is not the primary server for vlan database.

You need to set one of the switches in the VTP domain as the primary vtp server.

Image 1

Setting vtp mode server alone will not allow you to create VLANs. You will get an error when you try to create a VLAN:

image 2


VTP VLAN configuration not allowed when device is not the primary server for vlan database.

To correct this, as stated earlier, you need to configure a primary VTP server, as shown below in EXEC mode:

image 3

SW1#vtp primary force
This system is becoming primary server for feature vlan
*Oct 27 21:24:16.632: %SW_VLAN-4-VTP_PRIMARY_SERVER_CHG: aabb.cc00.0100 has become the primary server for the VLAN VTP feature

Once done you are then able to create vlans:

image 4

CCIE notes for EIGRP

Cisco Tips & Tricks

At last i have made up my mind to sit for ccie R&S written by early August. I am starting a tips & tricks section for dynamic routing protocols. I will start with EIGRP and then gradually move towards OSPF & BGP.

EIGRP uses DUAL ( Diffused update algorithm). Now what is DUAL? This fancy name is being used by cisco as a kind of marketing tool. Cisco calls EIGRP as a hybrid protocol. It has features of both distance vector & link state protocol. EIGRP topology table will always keep a feasible successor. Feasible successor is nothing but a backup route.

Lets say we have two links. One is 56k & other is a T1 link. Now EIGRP topology table will contain t1 as a primary route and 56k link as a feasible route. The difference between EIGRP and other dynamic routing protocols is that due to the…

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Differences between PVST and PVST+

CCIE, the beginning!

Behind the simple “plus” in PVST+ lurk quite subtle details that can make the difference between the two concepts very fuzzy, so the goal of this post is to give you a very brief explanation and I hope enough simple to grasp about PVST and PVST+ and their relationship with the standard IEEE 802.1q:

IEEE 802.1q standard

PVST (Per VLAN Spanning Tree) Cisco proprietary

PVST+ Cisco proprietary

BPDU transported over native VLAN untagged (cannot differentiate between different VLANs), therefore support natively only one single instance of STP for all VLAN, MST (Mono Spanning Tree).

(-) Not interoperable and less flexible approach.

(+) Improve the limitation of 802.1d STP (created before VLAN) by supporting one separate instance for each VLAN, using ISL trunk only.

(-) Still not interoperable with IEEE 802.1q that supports only one STP instance.

(+) Modification of PVST: allow PVST over standard IEEE 802.1q:

1) – PVST+…

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