> For the complete documentation index, see [llms.txt](https://jncia-workbook.gitbook.io/workbook/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jncia-workbook.gitbook.io/workbook/junos-routing-policy/7-selective-redistribution-part-1.md).
# 7) Selective Redistribution (Part 1)
### Pre-Work
Load the config called **policy.cfg** using the **load\_config\_on\_nodes.py** script.
```
python3 load_config_on_nodes.py --lab_dir three-routers --config_filename policy.cfg
```
### Lab
All routing (static routes, OSPFv2, and BGP) is already setup.
Configure R1 to redistribute all static routes into OSPF. Use a route policy that only permits prefixes within 10.0.0.0/16, and including 10.0.0.0/16.
### Answer
Expand to reveal
```
edit policy-options policy-statement STATIC_TO_OSPF
set from protocol static
set from route-filter 10.0.0.0/16 orlonger
set then accept
top
set protocols ospf export STATIC_TO_OSPF
```
### Explanation
Expand to reveal
Route policies allow us to have granular control over which prefixes are redistributed. In this lab, we use a `route-filter` to only permit prefixes within 10.0.0.0/16. A `route-filter` is defined "in-line" of the route policy.
```
edit policy-options policy-statement STATIC_TO_OSPF
set from protocol static
set from route-filter 10.0.0.0/16 orlonger
set then accept
```
\
The `orlonger` keyword means that we allow any prefix within `10.0.0.0/16`, including the prefix `10.0.0.0/16`. `orlonger` is referring to the mask, meaning we allow a prefix within this subnet with mask /16 or longer than that (up to /32). There are several other options besides `orlonger`, listed in the table below:
| Keyword | Meaning | Example |
| --------------------- | ---------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `exact` | Only the exact prefix. | `10.0.0.0/16 exact` matches 10.0.0.0/16 and nothing else |
| `orlonger` | Any mask that is longer than the prefix specified, including the prefix specified. | `10.0.0.0/16 orlonger` matches 10.0.0.0/16, 10.0.1.0/24, etc. |
| `longer` | Only prefixes that have a longer mask. | `10.0.0.0/16 longer` matches 10.0.1.0/24, and does not match 10.0.0.0/16 |
| `upto` | Only prefixes with a mask up to the given value. | `10.0.0.0/16 upto 24` would mean 10.0.0.0/16 matches, 10.0.1.0/24 matches, and 10.0.2.0/25 does not match. |
| `prefix-length-range` | Only prefixes with a mask within the range. | `10.0.0.0/16 prefix-length-range 18 to 24` would mean 10.0.0.0/16 does not match, 10.0.0.0/18 does match, 10.0.1.0/24 does match, and 10.0.2.0/25 does not match. |
| `address-mask` | Allows you to specify a non-contiguous mask, similar to IOS. |
10.0.0.0/24 address-mask 255.0.255.0 matches /24s in the format 10.x.0.0/24. For example it matches 10.1.0.0/24 but does not match 10.0.1.0/24.
The mask you use (for example /24 here) is the exact mask the prefix must have in order to match.
|
| `through` | Match a range of masks, but not subnets within that prefix. | `10.0.0.0/16 through 10.0.0.0/24` will only match 10.0.0.0/(16-24) exactly. 10.0.0.0/16 matches, 10.0.0.0/17 matches, etc. But 10.0.2.0/23 does not match. |
\
We should see that R1 is only redistributing these two prefixes:
```
admin@R1> show ospf database external
OSPF AS SCOPE link state database
Type ID Adv Rtr Seq Age Opt Cksum Len
Extern *10.0.0.0 10.0.0.1 0x80000001 6 0x22 0x1e7f 36
Extern *10.0.1.0 10.0.0.1 0x80000001 6 0x22 0x1389 36
```
### Further Reading