---
title: "Normalization"
description: "Traffic normalization adjusts selected packet properties before the final pass or block decision. Global defaults are available under Firewall ›…"
---

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# Normalization

Traffic normalization adjusts selected packet properties before the final pass or block decision. Global defaults are available under **Firewall › Settings › Filter**, while custom normalization is configured as part of **Firewall › Rules [new]**.

## Global settings

| **Option** | **Description** |
|----|----|
| **Enable scrub** | Enable default packet scrubbing and generated interface MSS rules. |
| **IP Do-Not-Fragment** | Clear the DF bit when fragmented IPv4 packets are reassembled. |
| **IP Random ID** | Randomize the identification field of IPv4 packets using a generated match rule. |

Filling in **MSS** on an interface under **Interfaces › Assignments** generates IPv4 and IPv6 normalization match rules for that interface. Disabling scrub also disables these generated rules.

## Rule normalization

Select the **Match** action to apply normalization without deciding whether traffic is passed or blocked. A **Pass** rule can apply the same options while also allowing traffic. Match rules follow the normal firewall rule ordering; they are usually not quick so evaluation can continue after their options have been applied.

The normalization fields are available in the advanced section of the rule dialog.

| **Option** | **Description** |
|----|----|
| **Clear DF bit** | Clear the don't-fragment bit on matching IPv4 packets. |
| **Random ID** | Replace the IPv4 identification field with random values. |
| **Maximum MSS** | Reduce the maximum segment size on matching TCP SYN packets. |
| **Minimum TTL** | Enforce a minimum TTL on matching IP packets. |
| **Set TOS / DSCP** | Set the TOS or DSCP value on matching packets. |

Source: https://docs.ixolate.com/firewall/normalization-scrub/index.mdx