FAQ

Is it possible to balance different types of links through the Elfiq Link Balancer?

Yes, you can use many possible combinations of links. Some basic examples include: a T1 link from one Internet service provider (ISP) and an xDSL link from another ISP, or two cable links from the same ISP and one xDSL link from a different ISP. 

What are the types of connections supported by the Elfiq Link Balancer?

The Elfiq Link Balancer offers standard Ethernet interfaces as interconnection points. Therefore, dedicated links, xDSL, cable, Frame Relay, fixed wireless, 3G/4G mobile, ISDN and more are all supported as long as a router encapsulates or converts the link traffic to Ethernet before it passes through the Link Balancer.

What happens with links of different speeds?

The Link Balancer can manage links of equal, different or asymmetric (different download and upload speeds) speeds just as well. Links of different speeds are managed transparently through the Link Balancer, which also guarantees that the most effective link is used for each given situation.

What is the performance level of the Elfiq Link Balancer?

The Elfiq Link Balancer offers a very high level of performance, as it can simultaneously manage multiple 100mbps links. The LB-400E model also supports gigabit links.

Is the Elfiq Link Balancer able to detect a link failure?

Yes, the Link Balancer monitors each of the WAN/Internet links in order to detect logical or physical problems. In the case of a failure on one of the links, the traffic will transparently be redistributed to the other links.

How will we know if there is a failure to one of the WAN/Internet connections?

In the case of a service rupture on one of the links, a syslog event will be sent to the syslog server preconfigured in the Link Balancer’s configuration. Optionally, an SNMP alert can also be sent.When a service rupture occurs, traffic is redirected to the other links. Most TCP applications will automatically retransmit the few packets that were lost during the transition. This will therefore make the loss of a link practically transparent to users and applications.

How is incoming traffic balanced?

Incoming traffic balancing is based on primary and secondary DNS entries that point to the client’s environment. Each session’s establishment or incoming protocol transaction will make a name resolution before establishing the session. The role of the Elfiq Link Balancer is to intercept those DNS queries and to respond based on link availability and other pre configured factors. Every service provided over the WAN/Internet links contains virtual DNS entries known as IDNS Resource Records (IDNS RR), and every IDNS RR entry is associated with an outgoing GMAC (WAN router). Many virtual DNS entries can be created in the Link Balancer in order to answer all incoming DNS queries.

How is outgoing traffic balanced?

Outgoing traffic balancing gives users and systems behind the firewall simultaneous access to multiple WAN/Internet links. All outgoing connections exit with addresses that have been translated through NAT or by a predefined address, such as a proxy. With the Elfiq Link Balancer, definitions of groups of IP addresses, known as poolIPs, allow real time dynamic outgoing access to a predefined WAN/Internet link. A network address translation (NAT) is then done intended for the WAN/Internet link.

How many WAN/Internet links can an Elfiq Link Balancer manage?

The Elfiq Link LB uses a concept similar to an Ethernet bridge called Virtual Forwarder Interface (VFI). A VFI is an association of an input and output Ethernet interface. The enterprise model can support up to 5 VFI. Each VFI can support between 2 and 320 links depending of the Elfiq Link Balancer model.

We have 2 WAN/Internet links but our firewall only supports one default gateway. How does the Elfiq Link Balancer manage traffic?

Since the Link Balancer operates at the data link layer of the OSI model (layer 2), it is practically invisible to the network. It detects, caches and manages the MAC addresses of the different WAN routers. Since the firewall only supports one default gateway, the Link Balancer will route the appropriate packets to the chosen router. The Link Balancer registers all the MAC addresses of the external routers and stores each of them under a GMAC. If one of the routers fails to answer ARP requests, the balancer will automatically answer them for it and redirect the packets to one of the available GMACs, as chosen in the configuration. Therefore, everything is transparent to the firewall.

Is NAT always required?

No, it is not always required to use network address translation. In fact, you can prevent the manipulation of certain protocols, such as IPSEC HA. You can also associate multiple IP addresses (aliases) with each server located in the demilitarized zone (DMZ). The remaining problem depends on the complexity of the firewall configuration.

We have multiple links on an Elfiq Link Balancer. How can we do maintenance on one of them without affecting all services?

All you need to do is deactivate the corresponding GMAC. This way, your configuration is not unmodified and the Link Balancer will continue to balance all the traffic on all the other links, except the one that has just been deactivated.

Does the Elfiq Link Balancer require access to the routers that face the WAN/Internet links?

No, the Elfiq Link Balancer manages transmitted packets and estimates link utilization per ISP by itself since access to the service providers’ routers in order to read statistics is usually blocked for security reasons.

Is it possible to be notified when a WAN/Internet link goes down?

Yes, by default Elfiq Link Balancer will send an alert in real time to the management station as well as to the configured syslog server.

Am I required to have an Autonomous System Number (ASN)?

No. A key factor in the Elfiq Link Balancer design is that it is easy to integrate, so no ASN is required to use the Elfiq Link Balancer.

How does the Elfiq Link Balancer detect a problem on a WAN/Internet link?

The Link Balancer checks the status of each WAN link every 3 seconds (default value). During that time, three TCP sessions are conducted for each of the destinations configured in an ISP.Therefore, every 3 seconds a SYN, SYN-ACK, RST sequence is done on each ISP, to the destination of the next hop for that link. The response time (RTT) to this hop is then calculated.If the first hop does not answer, the Link LB will try to contact the second hop. If the second one does not answer, the ISP is automatically deactivated and the network traffic is dynamically redistributed to the other links.