FreshTomato Wiki

The Firewall page allows you to configure options to protect or facilitate certain network communications.

\\ \\ **WAN interfaces respond to ping and traceroute:  **If enabled, this lets your device reply to ICMP ping and traceroute request packets from Internet hosts. This is necessary for //ping //and //traceroute to //work from the WAN/Internet.

Limit communication to: This setting/value is only enabled when the WAN interface(s) respond to ping and traceroute option is enabled. This sets the maximum number of requests per second to which the Firewall will reply. Setting a limit is advised to prevent DDoS attacks.




Enable TCP SYN cookies: Enabling this protects the router from SYN Flood attacks via the “SYN cookies” technique. This function encodes information from the SYN packet into the (SYN/ACK) response. Despite being a standard technique for preventing SYN floods, enabling this will create some secondary limitations which may cause issues with some old TCP/IP stacks.

Enable DCSP Fix - Checking this enables a workaround for a well-known issue related to DSCP (packet marking) when connected to Comcast.

IPv6 IPSec Passthrough - Enabling this allows IPSec tunnels to pass through the firewall. It opens UDP port 500 and the “ESP” protocol (IP protocol 50) to accomplish this.

NAT loopback - This technique is also known as “Hairpinning”. It allows LAN devices to communicate with each other via the router's WAN interface. This is commonly used when connecting to the DDNS domain of your router from the LAN. This legacy setting is rarely needed nowadays. It can create a speed bottleneck as wel.

• All
• Forwarded Only
• Disabled

NAT target - This defines the way NAT is implemented for use with NAT loopback. Masquerade is the default, however this involves an additional lookup and the mapping is done towards an interface. SNAT is minutely faster. Its NAT mapping points directly to the destination IP address and thus bypasses the lookup stage. However, SNAT is less reliable.

• Masquerade *
  • This is the most reliable method.
  • It is minutely slower than SNAT, due to extra overhead. Most networks will never see any speed difference.
  • The rule is not consulted for every packet, only the packet that initiates the connection. After that, packets in both directions are routed via the mapping table, as is done with NAT.
    
• SNAT: This method has a minute speed advantage, but at the cost of reliaibility.
  • SNAT uses the IP address of the WAN ( or other link interface ) at the time the rule is set in iptables.
  • If the IP address changes, and the rule is not changed to match, it will break.

Enable IGMP proxy - Runs the IGMP (Internet Group Management Protocol) service on the router.

LAN0/LAN1/LAN2/LAN3 - Specifies which bridges will be subscribed to partecipate in IGMP using the router as a proxy between the LANs selected. Essentially, this allows IGMP to work between VLANs.

Enable quick leave - This is a feature of IGMP v2. This allows the router to stop the streaming of a multicast to an IP address as soon as that end device sends the quick leave IGMP packet.

Custom Configuration - This option allows you to set up advanced parameters for the IGMP proxy daemon. Please consult the official IGMP documentation before finalizing these settings.

Enable Udpxy - Like IGMP proxy, Udpxy allows multicast communications between senders and receivers in different VLANs. Since their behavior is almost identical, it is recommended you use either Udpxy or IGMP proxy, but not both at the same time.

Upstream interface - Defines where the stream source is expected to live. (Default: blank).

LAN0/LAN1/LAN2/LAN3 - This is where the stream clients are expected to live.

Enable client statistics - Enabling this causes FreshTomato to collect statistical information about Udpxy clients.

Max clients - Considering this is a lightwave protocol it works well for a limited number of clients, you might want to impose a maximum number.Specifies the maximum number of simultaneous Udpxy clients.

Udpxy port- This is where you can consult the Udpxy information on your router.

Efficient Multicast Forwarding (IGMP Snooping) - IGMP snooping is a way to have the switch (part of the router) facilitating the discovery of multicast (IGMP) clients. The idea is to only multicast traffic towards ethernet ports where there's at least one group joiner (a.k.a. subscriber client). Beware, UPnP is often the only significant multicast application in use in digital home networks; therefore, multicast network misconfiguration or other deficiencies can appear as UPnP issues rather than underlying network issues. If IGMP snooping is enabled on a switch, or more commonly a wireless router/switch, it will interfere with UPnP/DLNA device discovery (SSDP) if incorrectly or incompletely configured (e.g. without an active querier or IGMP proxy), making UPnP appear unreliable. Typical scenarios observed include a server or client (e.g. smart TV) appearing after power on, and then disappearing after a few minutes (often 30 by default configuration) due to IGMP group membership expiring. On this very topic please beware of the wireless multicast forwarding under Advanced Wireless

Force IGMPv2 - IGMPv2 enhances the IGMP communication supporting additional messages/behavior to optimise the end-to-end communication between client and server. Possibly the most important being the “Group Leave” message which is lacking instead in IGMP v1.