stacking & redundancy

[eng_adel273]

I need to Know what is difference between both techniques.

How to apply them

[Julio E. Moisa]

Hi

Stacking is method to unify 2 or more switches and you will see them as one switch locally. It can provide redundancy as well. For example stacking could provide redundancy a server with 2 NICs, if a NICs fails the second will be used and you will not lose connectivity. 

Redundancy basically is associated to high availability where you lose connection to the services because you have a backup path so your downtime could be minimal. 

This link could be useful https://keepingitclassless.net/2011/12/redundancy-protocols-vs-stacking-pros-and-cons/

Hope it is useful

:-)

[eng_adel273]

can you tell me the steps configurations for creating stacking  & redundancy

[Meheretab Mengistu]

Basically, you will add redundancy by using Port-Channel interfaces. You will have ether-channel member interfaces from both switches (if you have two switches stacked together). So, when one of the switches goes down, you will still have connectivity.

HTH,
Meheretab

[Meheretab Mengistu]

Example:-

Stack two switches together, and check using "show switch". Once stacking is done, create layer 2 etherchannel interface as follows:

int gi1/0/1
switchport access vlan 10
switchport mode access
channel-group 1 mode on
!
int gi2/0/1
switchport access vlan 10
switchport mode access
channel-group 1 mode on
!

The above commands will create a layer2 "Port-Channel 1" as a member of vlan 10, with two member interfaces: Gi1/0/1 and Gi2/0/1 (from the two switches). For example, if you have a server on the other end with 2 NIC cards, the server will not loose its connectivity unless both switches (or both interfaces) are DOWN.

HTH,

Meheretab

[eng_adel273]

Thank you for your support

in my switch , there are the following commands  , what is the benefits

redundancy
 mode sso

[Meheretab Mengistu]

It enables SSO (Stateful SwitchOver) to the standby switch.


SSO Operation
When a standby switch runs in SSO mode, the standby switch starts up in a fully-initialized state and synchronizes with the persistent configuration and the running configuration of the active switch. It subsequently maintains the state on the protocols listed below, and all changes in hardware and software states for features that support stateful switchover are kept in synchronization. Consequently, it offers minimum interruption to Layer 2 sessions in a redundant active switch configuration.

If the active switch fails, the standby switch becomes the active switch. This new active switch uses existing Layer 2 switching information to continue forwarding traffic. Layer 3 forwarding will be delayed until the routing tables have been repopulated in the newly active switch.

Note
SSO Layer 2 Only is supported if the IOS-XE software is running the LAN Base license level.
The state of these features is preserved between both the active and standby switches:

802.3
802.3u
802.3x (Flow Control)
802.3ab (GE)
802.3z (Gigabit Ethernet including CWDM)
802.3ad (LACP)
802.1p (Layer 2 QoS)
802.1q
802.1X (Authentication)
802.1D (Spanning Tree Protocol)
802.3af (Inline power)
PAgP
VTP
Dynamic ARP Inspection
DHCP snooping
IP source guard
IGMP snooping (versions 1 and 2)
DTP (802.1q and ISL)
MST
PVST+
Rapid-PVST
PortFast/UplinkFast/BackboneFast
BPDU guard and filtering
Voice VLAN
Port security
Unicast MAC filtering
ACL (VACLS, PACLS, RACLS)
QOS (DBL)
Multicast storm control/broadcast storm control
SSO is compatible with the following list of features. However, the protocol database for these features is not synchronized between the standby and active switches:

802.1Q tunneling with Layer 2 Protocol Tunneling (L2PT)
Baby giants
Jumbo frame support
CDP
Flood blocking
UDLD
SPAN/RSPAN
NetFlow
All Layer 3 protocols on a switch are learned on the standby switch if SSO is enabled.

If you want to read further, please look at
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/3se/ha_stack_manager/configuration_guide/b_hastck_3se_3850_cg/b_hastck_3se_3850_cg_chapter_011.html


HTH,
Meheretab

[eng_adel273]

thank you very much for your support & efforts

I've one question

Why if i change IP address for example port 20 in switch 1 ( active )  , it not replicated to switch2 (standby) , port 20

[Meheretab Mengistu]

You are very welcome!

Each switchport is standalone port. If you have 2x Cisco 3850s with 48 ports each, you will have a 96 port switch after stacking. So, if you want Gi1/0/20 and Gi2/0/20 to be backup of each other, the way to do this is using Port-Channel configuration. Configure a Layer3 port-channel interface and add both ports as member interfaces.

Example:-

int Gi1/0/20
no switchport
channel-group 10 mode on
no shut
exit
int Gi2/0/20
no switchport
channel-group 10 mode on
no shut
exit
int Po10
ip address x.x.x.x 255.x.x.x
no shut
exit


PS:- If your question is answered, please do not forget to rate and accept the solution to help others with similar question.

HTH,
Meheretab

[eng_adel273]

Thank you for your help

in your configurstion

int Po10
ip address x.x.x.x 255.x.x.x
no shut
exit

in my configuation

interface Port-channel4
 switchport mode trunk
!

Is it possible to make trunk without IP address ?

[eng_adel273]

no switchport , what is command used for ?

[Meheretab Mengistu]

"no switchport" is used to make the interface Layer 3. By default, switch interfaces are Layer 2 (you can not assign IP address and other layer 3 features).

We could have Layer 2 and/or Layer 3 port-channels. If you want to assign IP address to the Port-Channel, it should be a layer 3 Port-Channel. If you do not need to have IP address on the port and prefer to use it as a Layer 2 trunk port, you do not need to change your configuration on Po4. The only thing you need to remember is to add member interfaces from both switches (if you stack two switches) so that you will have redundancy.

P.S.:- If your question is answered, please don't forget to rate it and accept the correct response as a solution to help others with similar question.

HTH,
Meheretab