Three way handshake includes SYN, SYN ACK, ACK. Close connection with FIN, FIN ACK or TCP RESET.

Web 80
FTP 21

Load balancers offer tremendous benefits by improving server farm availability, scalability, manageability, and security. Server load balancing is the most popular application for load balancers. Load balancers can perform a variety of health checks to ensure the server, application, and the content served are in good condition. There are many different load-distribution algorithms to balance the load across different types of servers in order to get the maximum scalability and aggregate processing capacity. While stateless load balancing is simple, stateful load balancing is the most powerful and commonly used load-balancing method.

Network address translation forms the foundation for the load balancer’s processing. There are different types of NAT, such as destination NAT and source NAT, that help in accommodating a variety of network designs with load balancers. Direct Server Return helps in load-balancing applications with complex NAT requirements, by obviating the need for destination NAT.

ERS Access to SMLT Core:

MLT

mlt 1 name “Trunk #1” enable member 49-50
mlt 1 advance
SPT disabled when connect to IST SMLT cluster

VLACP enabled.

MSTP backwards compatible with RSTP. MSTP instance 0 (CIST) = RSTP.

STPG (ERS)

spanning-tree stp 1 priority 1000 (primary root bridge)
OR
spanning-tree stp 1 priority 2000 (backup root bridge)

Interface Ethernet ALL
spanning-tree port 1 learning normal
spanning-tree port 2-48 learning fast
Exit

Non SSH image:

RO user
RW secure

SSH image:

RO userpasswd
RW securepasswd

After upgrading from non-secure image the non SSH defaults apply!

Gratuitous ARP is a sort of “advance notification”, it updates the ARP cache of other systems before they ask for it (no ARP request) or to update outdated information.

When talking about gratuitous ARP, the packets are actually special ARP request packets, not ARP reply packets as one would perhaps expect. Some reasons for this are explained in RFC 5227.

The gratuitous ARP packet has the following characteristics:

Both source and destination IP in the packet are the IP of the host issuing the gratuitous ARP
The destination MAC address is the broadcast MAC address (ff:ff:ff:ff:ff:ff)
This means the packet will be flooded to all ports on a switch
No reply is expected
Gratuitous ARP is used for some reasons:

Update ARP tables after a MAC address for an IP changes (failover, new NIC, etc.)
Update MAC address tables on L2 devices (switches) that a MAC address is now on a different port
Send gratuitous ARP when interface goes up to notify other hosts about new MAC/IP bindings in advance so that they don’t have to use ARP requests to find out
When a reply to a gratuitous ARP request is received you know that you have an IP address conflict in your network
HSRP, VRRP etc. use gratuitous ARP to update the MAC address tables on L2 devices (switches). Also there is the option to use the burned-in MAC address for HSRP instead of the “virtual”one. In that case the gratuitous ARP would also update the ARP tables on L3 devices/hosts.