Using Ip And Mac Address Masks - Dell Networking N4000 Series Configuration Manual

Stackable layer 2 and 3 switches

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Table 20-3. Common IP Protocol Numbers (Continued)

IP Protocol Number

Using IP and MAC Address Masks

Masks are used with IP and MAC addresses to specify what should be

considered in the address for a match. Masks are expanded internally into a

bit mask and are applied bit-wise in the hardware even though they are

entered in decimal or hexadecimal format. Masks need not have contiguous 0

or 1 bits. A 0 bit value in the mask indicates that the address field in the

packet being compared must match the address bit exactly. A 1 value in the

mask indicates a wildcard or don't care value, i.e. the access bits are not

compared and match any possible value. For example, an IP address of 3.3.3.3

with a mask of 0.0.0.0 indicates that the ACL matches on all four bytes of the

IP address. Likewise, a MAC address of 68:94:23:AD:F3:18 with a mask of

00:00:00:00:00:ff indicates that the first five bytes must match (e.g.,

68:94:23:AD:F3) and the last byte may take on any value from 0x00 to 0xff

(0–255) and still be considered a match.

The following ACL equivalents are noted:

255.255.255.255

ff:ff:ff:ff:ff:ff

Configuring Access Control Lists

Equivalent Address

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