The Firewall page allows you to configure options to protect or facilitate various types of network communications.

WAN interfaces respond to ping and traceroute: lets your device reply to ping/traceroute request packets from Internet hosts. This is needed for ping and traceroute to work via the Internet. Enabling this also may be needed for proper functioning of some VPN and IPv6 protocols.

Limit communication to: specifies the maximum number of requests per second to which the Firewall replies. Setting a limit is recommended to prevent DDoS attacks.

Enable TCP SYN cookies: uses “SYN cookies” to protect the router from SYN Flood attacks. It encodes information from the SYN packet into the (SYN/ACK) response. It is a standard method for preventing SYN floods. However, it has limitations that may cause issues with some old TCP/IP stacks.

Enable DCSP Fix: enables a workaround for packet marking, a well-known DCSP issue when using Comcast.

Allow DHCP Spoofing:

Smart MTU black hole detection:

NAT loopback: This allows LAN devices to access each other via the router's WAN interface. Also known as “Hairpinning”, it's often used when connecting to the DDNS domain of your router via the LAN. These days, this setting is almost never needed. Also, it can create speed bottlenecks.

• All
• Forwarded Only
• Disabled

NAT target - defines how NAT is implemented when in a loopback situation. Masquerade is the default, but involves an additional lookup, and the mapping is done towards an interface. SNAT is minutely faster, as its NAT mapping points directly to the destination IP and thus bypasses the lookup stage. However, SNAT is less reliable than Masquerade.

Enable IGMP proxy - Checking this enables the Internet Group Management Protocol service.

LAN0 - LAN3 specifies which bridges will participate in IGMP, with the router acting as a proxy between chosen LANs. This lets IGMP work between VLANs.

• LAN0 - Causes the LAN0 bridge to participate in IGMP proxy.
• LAN1 - Causes the LAN1 bridge to participate in IGMP proxy.
• LAN2 - Causes the LAN2 bridge to participate in IGMP proxy.
• LAN3 - Causes the LAN3 bridge to participate in IGMP proxy.

Enable quick leave - This IGMP v2 feature lets the router stop streaming multicast to an IP as soon as that device sends a “quick leave” IGMP packet.

Custom Configuration - Lets you set advanced parameters for the IGMP proxy daemon. Consult official documentation before using this.

Enable Udpxy - Like IGMP proxy, Udpxy allows devices on different VLANs to have multicast communications. Since they are similar, you should use either Udpxy or IGMP proxy, but not both at once.

Upstream interface - Here, enter the stream source is expected to live. (Default: blank).

LAN0/LAN1/LAN2/LAN3 - Specifies the location the streaming clients are expected to be found.

Enable client statistics -Ccauses FreshTomato to collect statistics about Udpxy clients.

Max clients - The maximum number of simultaneous Udpxy clients. Since Udpxy is is a lightweight protocol, it works well for a limited number of clients. Therefore, you might want to impose a maximum limit.

Udpxy port- Specifies the port on which you can recive Udpxy information from your router.

Efficient Multicast Forwarding (IGMP Snooping) - IGMP snooping makes the router's switch facilitate discovery of Multicast IGMP clients. This helps to send multicast traffic only towards ports with at least one multicast subscriber, reducing overall multicast traffic.

However, caution is advised. IGMP Snooping can interfere with functioning of UPnP or DLNA. This can make Multicast configuration errors or deficiencies appear as UPnP issues. Enabling IGMP snooping on a router's/switch interferes with UPnP/DLNA device discovery. Specifically, it can interfere with SSDP protocol transmissions. If IGMP snooping is incorrectly or incompletely configured (say, without an active querier or IGMP proxy), this make UPnP appear unreliable.

A common symptom of this is a network host (say, a Smart TV) which appears after it's powered on, but then “disappears” from the network after a few minutes. To be more precise, typically 30 minutes. This is because the default setting for when IGMP group membership will expire. Please be aware of the wireless multicast forwarding setting in the the Advanced/Wireless menu.

Force IGMPv2 - IGMPv2 enhances IGMP with additional messages/behavior to optimize end-to-end client-server communication. Perhaps the most important of these is the “Leave Group” message. When a host wants to stop listening to a multicast group address, it will report to the router that it has stopped listening. In v1, the host simply stopped listening, without informing the router.

Other features of IGMPv2 include:

Group specific membership query: Now, the router can send a membership query for a specific group address. When the router receives a leave group message, it will use this query to check if there are still hosts interested in receiving the multicast traffic.

MRT (Maximum Response Time) field. This new field in query messages specifies how much time hosts have to respond to the query.

Querier election process. When two routers are on the same subnet, only one should send query messages. Having an “election” process ensures only one router, with the lowest IP address, becomes the active querier.